16 Celebs We Completely Forgot Guest-Starred On Grey's Anatomy

After 14 years on the air with extreme success, there have been an endless amount of guest-stars coming and going on ABC's Grey's Anatomy. It has even launched the careers of some of its lead actors like Ellen Pompeo, Sandra Oh and Eric Dane in addition to making them household names. Every week, we become so invested in these core characters as well as the patients and families that they help treat.

For each one that passes away, bleeds, suffers, or loses, we shed an extra tear and cry, “Why Shonda, why do you do this to us?” The amazing thing about television shows with such extreme longevity is that they are bound to attract up-and-coming stars or even established ones who are current fans. There is a bevy of actors who-at the beginning of their careers-landed guest stints on Grey's Anatomy. At the time, they may have left you sobbing, but now after all of these seasons, you may have forgotten that they were ever even on the show. You are about to be amazed by the 15 guest stars you completely forgot ever graced the halls of Grey Sloan Memorial Hospital. Prepare yourself to be stunned!

16 This Patient Needed A Blood Transfusion

By season six in 2010, Mandy Moore was already a household name in both the music industry and Hollywood. Her pop hit Candy put her up in the ranks with Britney Spears and Christina Aguilera. Her turn as dying student Jamie Sullivan in A Walk to Remember secured her as a beautiful young actress to watch, but it was her turn as a patient Mary Portman-who needed colostomy bag reversal surgery-that deemed her ready for primetime.

This was several years before she was appropriately cast as matriarch Rebecca Pearson on NBC's smash-hit series 'This Is Us'.

The character entered the hospital with her husband Bill but was told by Dr. Bailey that she would need a blood transfusion first in order to go any further. Part of Moore's four-episode arc included her being on lockdown in the hospital with a crazed shooter and-ultimately-assisting Bailey with a surgery, per ABC.

She ended up leaving with her husband only to return six months later when Bailey was able to perform the bag reversal. Unfortunately, Mary did not wake up from anesthesia and ended up passing away from organ failure. Around the same time Mary Portman passed, Moore was resurrected as Rapunzel in Disney's highly successful film, Tangled.

15 The Doctor That Led Arizona To Cheat

By the time Hilarie Burton started her brief season nine stint in 2013 as Dr. Lauren Boswell, she had already experienced extensive television fame. It truly started with a six-season lead role on the hit teen series One Tree Hill where she played Peyton Sawyer and three seasons as Sara Ellis on White Collar. She really spiced things up when she played the doctor who came in between Arizona and Callie, the lesbian power couple of the show. Fans did not take her entrance sitting down.

After the promo aired with Hilarie and Jessica Capshaw-who played Arizona up until this current season-and the title of Unfaithful, Burton revealed to the Huffington Post some of the fan reactions. A few fans included death threats due to their devotion to Callie and Arizona's marriage-and their disfavor to the idea of someone new stirring the pot.

Though Burton admits she is not the kind to come in and flirt with a married person, she believes Lauren has a good heart. Arizona and Lauren did ultimately have relations after a strenuous NICU procedure, but Arizona confessed she loved Callie and away Lauren went. Hilarie-on the other hand-is a wife and mother of two kids, having just given birth to her first daughter quite recently.

14 The Little Girl Who Helped Save Her Mom's Life

Playing Eleven on Stranger Things would have to wait just a short time because Millie Bobbie Brown (as she was credited at the time) would have to make a quick stop at Grey's-via telephone, that is. In the 2015 season 11 episode entitled I Feel the Earth Move,

Millie played a young girl named Ruby whose mother falls during an earthquake.

Ruby calls the hospital where Owen, April and Amelia work tirelessly to attempt to get the call traced back to the cabin in which Ruby and her mom are staying.

Unfortunately, without a landline, this makes it quite difficult as her mom is beginning to turn blue around the lips. The doctors realize that they have to be quite delicate with the mother as she could become paralyzed but would rather her paralyzed and alive than die in front of Ruby. They help work the young girl through the procedure even having her sing Stayin' Alive to coach her through-but her phone goes dead. They ultimately do arrive at the cabin and mom receives the treatment that she needs, all with the help of some dedicated doctors and a faithful daughter, Entertainment Weekly reports. This was all training for the crazy success Millie was about to experience when Stranger Things exploded in 2016.

13 Derek's Doctor Sister, Lizzie

Neve Campbell had already completed four Scream films and had spent six seasons on the wildly successful FOX family drama Party of Five as Julia Salinger by the time she entered Grey's Anatomy as Dr. Lizzie Shepherd. Coming aboard as one out of four of Dr. Derek Shepherd's sisters in 2012 during season nine, her primary job was to try to convince her stubborn surgeon brother-actor Patrick Dempsey-to get surgery on his nerve-damaged hand, according to Huffington Post.

She spent two episodes attempting to bond with her family and make some sort of impactful case on Derek, as did all of his loved ones. Interestingly enough, fans may recall that this is not the first time where Campbell and Dempsey have teamed up. They both co-starred in the third installment of the Scream franchise-which was released in 2000-just five years prior to Grey's debut.

Upon exiting the show, Campbell starred in films including Walter and is currently filming Skyscraper. What we loved was seeing how many doctors existed in the Shepherd family, because that is a lot of knowledge. We wonder if we will see Lizzie return now that Derek is gone considering we are down a Shepherd.

12 He Passed Right After He Got Engaged

He comes into homes on Sunday nights and scares the bajeebees out of 'The Walking Dead' fans in his leather jacket, scuffed boots, worn jeans, and barbed wire baseball bat. Negan is a force to be reckoned with, but there was a time when his portrayer-Jeffrey Dean Morgan-was one of the most lovable guest-stars in 'Grey's' history.

For over 20 episodes-season two through three, then in flashbacks for season five-Morgan's portrayal of Denny Duquette captured hearts around the world.

He came in to receive a heart transplant but what he really won was Dr. Izzy Evans' heart-portrayed brilliantly by Katherine Heigl. Their story was lovely, tear-jerking and memorable, and it culminated in a hospital proposal.

Shortly after Izzy agreed to marry Denny, he ended up suffering a stroke and passing away, literally leaving Izzy a shell of her former self-sobbing in her pink dress, E! Online. He did ultimately gift her with over $8 million to which she used to open her own clinic, an extension of the hospital. It is still considered one of the saddest deaths of the series and now-fast forward to 2016-and Morgan's Negan is delivering some of the most devastating TV deaths. As a side note, Morgan's now-wife Hilarie Burton played the doctor who caused Arizona to cheat on Callie.

11 The Doctor Who Left Blind

Geena Davis has had a long and successful career that includes Thelma and Louise, Beetlejuice and A League of Their Own. She has even taken home an Academy Award, per IMDb. All this being said, her turn as dying Dr. Nicole Herman for 12 episodes during season 11 and 14 helped bring her back to television after her show Commander in Chief was canceled back in 2006.

Just a short time later, Davis accepted the lead role on the television adaptation of The Exorcist. Anyway, how did her character impact the Grey's series during those 12 episodes? She was specifically impactful due to her role as somewhat of a mentor to Dr. Arizona Robbins, with whom she chose to share her deep medical knowledge. This was her way of passing her legacy down to the appropriate person.

Dr. Herman believed Arizona was the perfect person for this. Fortunately, she had life-saving surgery to remove her brain tumor-but it did leave her blind. Therefore, she was off recovering at an institute. However since Jessica Capshaw-the portrayer of Arizona-is exiting this season, and Geena Davis is returning. Many are speculating that this means she may be playing a part in Arizona's departure. That would be an extremely exciting twist.

10 She Wasn't Really Crazy-It Was Literally In Her Head

Demi Lovato had already struck gold as Angela on Barney & Friends, Mitchie on Camp Rock and Sonny on Sonny with a Chance, but her season six turn as Hayley May showed Lovato's true acting chops. Admitted to the psychiatric ward as a paranoid schizophrenic in 2010, Dr. Alex Karev could tell that there was something more to Hayley than met the eye. After doing some more research and probing-while Hayley attempted to hurt herself with a large syringe-it was discovered that she actually had Superior Canal Dehiscence Syndrome. This amplifies sound in the inner ear, thus increasing sensitivity.

The finding led Karev to perform the proper surgery to cure the condition-after which everyone realized that Hayley had been royally misdiagnosed.

Interestingly enough the same year this episode was filmed, Lovato found herself seeking help for similar issues to her character, according to Refinery 29.

She has been extremely public about her battles and struggles and has broken the stigma. In a way, the casting seemingly foreshadowed what we would see not too far down the line in the actress/singer's personal life. She came out swinging with comeback songs like Skyscraper and Cool 4 the Summer as well as hit albums Unbroken and Confident, giving young girls and women the ability to feel beautiful in whatever skin they are in. Interesting how life imitates art.

9 What's A Patient Without Insurance?

Just one year before he officially became a part of ABC's TGIT, Scott Foley had a 15-episode stint playing the role of Henry Burton. Interestingly enough, this was not the first time he worked with Patrick Dempsey, better known as Dr. Derek Shepherd. The two appeared alongside another Grey's guest star-Neve Campbell in 2000's Scream 3-so it was a reunion of sorts.

Foley's character of Henry Burton was gentler than the demon he portrayed in Scream. He came to the hospital needing medical care but did not have insurance to cover what he needed. The doctors tried to help the best that they could, but unfortunately, it was not enough. That was when surgeon and mentor Teddy Altman offered to marry him so that he could go under her health insurance. He declined but being a faithful doctor; she would not take no for an answer. They married, though she pursued other men, per ABC.

Eventually, he did not need her insurance, but they did need each other. Sadly, he ended up dying during surgery in 2012. However, Foley moved on by playing Jake Ballard for five seasons on the hit series Scandal, so it is safe to say that-though his character's fate was bleak-his real-life fate was pretty strong.

8 Protective Mama's Girl

The Handmaid's Tale has garnered Elisabeth Moss a Primetime Emmy award, IMDb reports, but it was Mad Men that initially made her a household name. The same year that show came debuted-2007-was the same year Moss made an appearance as Nina Rogerson during season three of Grey's as a doting daughter who took care of her mother. Her mother had to undergo a dangerous surgery that could cause her to bleed out in the process, but despite being extremely cautious, Nina's mother went through with it.

Unfortunately, she died during the surgery, however, Nina was informed that her mother wanted her to go on and live her life-regardless of what happened during the procedure.

We do not know what happened to Nina, but we do know that Elisabeth followed up her guest appearance with her role of Peggy Olson on 'Mad Men', garnering her several award nominations.

Also, a few film roles such as Daphne Binks in Get Him to the Greek and Phyllis Wepner in Chuck. We also cannot forget the amazing accolades she is continuously receiving through the television adaptation of The Handmaid's Tale, where she portrays June Osborne and serves as a producer on the show.

7 Meredith's Rejected Vet

Chris O'Donnell has starred on NCIS: Los Angeles as G. Callen since 2009, but before landing small screen success, he was known for his big-screen roles in Scent of a Woman, Batman & Robin and Vertical Limit. It was his stint as Dr. Finn “McVet” Dandridge for nine episodes during 2005 through 2006 on Grey's that gave him a taste of being on a successful nighttime drama. He came in during season two as a vet when Derek Shepherd's pup was sick.

While keeping both Meredith and Derek apprised of the situation on the dog, he started to fall for Meredith-as did she. Meredith even invited him to the prom. However, she left and slept with Derek, leaving Finn in the dust. Though he was extremely persistent, and she was wooed by his charming ways, Meredith was still attached to Derek-torn as she was.

Finally, Finn let her know that Derek would probably break her heart in the end but he would not be there to pick up the pieces. Ultimately, Meredith and Derek did end up getting married, according to ABC. That took so much time and turbulence, though. Maybe it would have been better to keep things going beyond season three with the vet, but then we would not have the show we know and love today.

6 Dishonest Mother Beatrice

During season two, Laurie Metcalf already had an extremely long resume (and Primetime Emmy's to boot!). She was best known for her role as Jackie Harris on Roseanne for nine seasons and Mrs. Davis-aka Andy's mom in the Toy Story films.

She took on a more serious character in her 2006 episode as Beatrice Carver.

Her role was of a mother with terminal cancer who had yet to inform her daughter that she was not only sick but that she was dying. This is not an easy situation for any mother and Metcalf can attest to this, being a mother herself.

If the character of Beatrice taught us anything, it is always to be honest with our loved ones because tomorrow is never promised. Therefore, be grateful for today. After Grey's, the actress went on to star in Desperate Housewives and as Sheldon's overly religious mother Mary Cooper on The Big Bang Theory. In 2018, she reprised her role as Jackie Harris and the cast of Roseanne reunited for a tenth season-which has been incredibly successful and already renewed for an eleventh season. She was also nominated for an Academy Award but lost out to equally talented Allison Janney, according to Gold Derby.

5 Guitarist With MS Falling In Love

Ten years after he left his role as Fez on That '70s Show and four years after the end of Handy Manny, Wilmer Valderrama stepped into the more serious role of Kyle Diaz. This part would last him five episodes and forge an unlikely romance with Dr. Stephanie Edwards. A guitarist with MS who entered the hospital during season 12 for hand tremors, he had a series of surgeries in order to attempt to curb the tremors in both hands.

Eventually, despite being on tour, he came back to the hospital and ended up passing away in the OR, leaving Dr. Edwards devastated, per Popsugar. Haven't they learned not to get involved with patients yet? Interestingly enough, Valderrama's real-life on and off again love interest Demi Lovato made a guest appearance on the show as well-but her character made it out alive.

Wilmer's television career was just getting revived as he now stars as Special Agent Nicholas “Nick” Torres on NCIS: New Orleans, is back in film as Sam in To Whom It May Concern and as Prince Charming in Charming. As for Dr. Stephanie Edwards, she is no longer a part of the hospital anymore. She exited at the end of season 13.

4 A Postmortem Surprise

Everybody remembers Doris Roberts as Ray Romano's overbearing mother Marie Barone for 210 episodes on Everybody Loves Raymond. It was her dramatic yet charitable turn as Gladys Polcher during season seven in 2011 that continued to warm hearts across the world. Though the late Ms. Roberts--who passed away in 2016, CNN reports-had an extensive resume filled with all kinds of interesting characters, her character on Grey's was unfortunately battling lung cancer. Dr. Alex Karev-played by Justin Chambers-was attempting to gather together money for his orphaned children's fund. He discovered that Gladys was a wealthy woman, so he approached her about a donation-fantastic bedside manners, Dr. Karev.

Eventually, she passed and he did not see a dime until her estate sent him a check for $200,000-very reminiscent of what happened when Izzy received the eight million dollars from Denny postmortem.

After Doris' stint on the show, she continued acting on the small screen on shows such as 'Melissa and Joey' and 'Desperate Housewives'.

She also starred in films that included Merry Kissmas and Madea's Witness Protection. Her legacy lives on through her larger than life roles and even bit roles like that of Gladys on Grey's because-in the end-they left an impact on the core characters as well as our hearts.

3 The Reluctant Kidney

If you have seen Hamilton on Broadway, you undoubtedly know Leslie Odom, Jr. Even if you have just heard the soundtrack, you know the booming voice and impact he has had on this generation. Before Odom landed his big Broadway break, the actor was playing a reluctant kidney donor on season five. IMDb notes he had several recurring roles prior to his 2008 stint as P.J. Walling, including Joseph Kyle on CSI: Miami, Agent Malik Christo on Vanished and Freddy on Big Day.

Aside from CSI: Miami, Grey's was a big booking for the then 26-year-old. In the episode, his father is in dire need of a kidney transplant and of course, Odom's character P.J. is the match and does not want to be the one to go through with the donation. Eventually, he realizes this is what he has to do and that he can save his father. He undergoes the kidney removal and donates it to his father. The good deed on the show translated to real life as Odom went on to star as Sam Strickland in Smash, Reverend Curtis Scott on Law & Order: SVU and of course, Aaron Burr in Hamilton, which garnered him a Tony Award. He is a prime example of making magic.

2 No Feelings-Can You Fix Me?

Abigail Breslin felt anything but sunshine when she was admitted to the hospital in season three as Megan Clover. This particular character could not feel any pain so she would inadvertently hurt herself because she did not know what she was doing. The year was 2006, and this came shortly after her portrayal of Bo Hess in the horror film Signs and Sarah Davis in the Kate Hudson-helmed comedy Raising Helen, per IMDb.

It was also the same year she danced her way into our hearts as awkwardly adorable Olive Hoover in 'Little Miss Sunshine'.

On the episode of Grey's, she kept getting hurt. Although it looked like her foster parents were the ones causing the bruising, it was actually a disorder typically discovered in babies. Scared she would be put back into the system because she had something wrong with her, she hid the fact that she felt no pain from her parents.

After a successful surgery, she was fine and able to go home and be a normal kid. Unlike her character, Breslin kept on working and showed up as Maya Hayes in Definitely, Maybe, Hailey Doyle in New Year's Eve and as a main character in the now-defunct television show Scream Queens.

1 He Was A Little Deaf Boy With A Big Goal

Dylan Minnette never could've imagined where a stint like this one on a season four episode of Grey's would land him one day. The fuller-faced, younger teenage heartthrob had only a few short credits to his name prior to his role as Ryan-a child born with no external ears.

Leave it to another hearththrob-Dr. Mark Sloan, played by Eric Dane-to come to the rescue. The child of a cafeteria worker at then-Seattle Grace, Ryan, and his mother were grateful beyond measure for the outpouring of interest the surgical team had in making this boy feel like he finally felt in with the rest of the world. The Odyssey Online reports Minnette is commonly remembered by Grey's fans as the little boy who went trick-or-treating to earn his surgery-no a far stretch from the truth as Meredith escorted him around the hospital plucking surgeons to build his reconstructive team of masterminds.

In keeping with tradition, Shondaland would go on to cast Minnette as the son of President Grant and his wife, Mellie in Scandal. But nothing could prepare Dylan for the role that catapulted him into the spotlight playing Clay Jensen in the hit Netflix series 13 Reasons Why. Season two just hit screens. Go catch up!

References: ABC, Entertainment Weekly, Huffington Post, E ! Online, IMDb, Refinery 20, ABC, IMDb, Gold Derby, Popsugar, CNN, IMDb, IMDb, Huffington Post, Cosmopolitan, Hollywood Reporter, E Online, Entertainment Weekly, Billboard, Odyssey Online