Remember them?

As the years have gone by, we've seen a number of famous fan familiar faces pass through the doors of Seattle Grace/Seattle Grace Mercy West/Grey Sloan Memorial hospital. Some of them had longer arcs on the show while others had a more brief-but-memorable appearances. But, in a show where there's a disaster every week, we wouldn't blame you for not necessarily remembering them. In honour of season 15, we decided to look back on some of our favourite Grey's Anatomy guest stars.

Dylan Minnette

Pre-13 Reason's Why, the actor featured in a season four episode as Ryan, a young boy who was born with no external ears - but had the internal structure to hear. He arrived at the hospital one Halloween in search of Mark Sloan, encouraging the doctor to build him ears for free. While Mark offers this time, he admitted they needed other things - and he didn't have the right network to ask for them. So Meredith and Ryan went trick-or-treating around the hospital, in search of all the things he needed for the ears. They were able to get together a team, and Mark reconstructed Ryan's ears.

Millie Bobby Brown

Way before she was in the Upside Down, Millie Bobby Brown played a girl named Ruby in a season eleven episode

The dramatic episode saw the young girl try to save her unconscious mum after she falls during an earthquake. The doctors coach Ruby on what to do via the phone, since they can't get to them to help.

When they find out that her mum's airways are blocked, they have Ruby pierce her mum's throat to release the trapped air and perform CPR. In the end, they airlift the mother-daughter duo to the hospital - where Ruby finds out she saved her mum's life.

Abigail Breslin

The Little Miss Sunshine star played Megan Clover, a little girl found to be insensitive to pain, back in season three.

After falling on the playground and cutting open her leg, Megan's foster parents rushed her to the hospital. Her history of injuries and accidents immediately worry the doctors, leading them to suspect she had been abused.

But it turns out that her injuries were due to congenital insensitivity to pain with anhidrosis (CIPA), which led to her doing things like letting one of her classmates hit her in the stomach with a baseball bat (which she also had a successful surgery to fix the internal bleeding it caused).

Kyle Chandler

Before he was Coach Taylor on Friday Night Lights, the actor featured in a number of episodes in as bomb squad member Dylan Young - two of his appearances were in his ghost form, though. Dylan first appeared as season two as he tried to help Meredith and Burke remove a bomb from a  man's torso. But after Meredith hands over the device and Dylan heads  out of the OR, the bomb explodes - killing him instantly. He later appears in season three when Meredith has her near death experience after falling into Elliot Bay.

Elisabeth Moss

Pre-Mad Men and The Handmaid's Tale, Elisabeth Moss played Nina Rogerson, a woman who accompanied her mum Cathy to the hospital in season three. Nina was incredibly protective over her mum, who had a condition that caused bone to grow at the sign of any trauma. Cathy was told by the doctors that she may bleed to death if she did not undergo a risky surgery. She had the procedure, as that's what Nina wanted to do, but passed away in surgery.

Liza Weil

The Gilmore Girls star featured in a season five episode as Alison Clarke, a cancer patient who Izzie meets in treatment. While the college student had been responding well to the experimental IL2 treatment at first, things took a turn when she randomly coded one day and had to be rushed to surgery. The doctors tried desperately searched for a bowel perforation in a bid to save her, but didn't find anything - and were ultimately unable to finish the procedure after she became unstable. She was unable to come off the ventilator after her surgery, and her loved ones were told she wouldn't wake up.

Jesse Plemons

The Black Mirror star featured as Jake Burton, a patient with craniodiaphyseal dysplasia, back in season two. The bone disorder cause calcium to build up in the skull, which can lead to facial disfiguration. Jake's case saw the growth move inward, as well, and Derek was tasked with removing his brain tumour. He ended up passing away during surgery.

Sarah Chalke

The former Scrubs star played Casey Hedges, a mum who was desperately trying to advocate for her young son, Parker. The little boy was repeatedly misdiagnosed with "minor" illnesses, as well as other viruses and strep throat. But, at the final moments, Meredith figured out that Parker had a rare syndrome called Kawasaki disease - and was able to save his life. Chalke's storyline on the long-running medical drama was based off a real life experience she had with her son.

Maggie Siff

The Son's of Anarchy star played Ruthie Sales, a woman came into the clinic with severe osteoporosis caused by malnutrition. She had fallen on the stairmaster and injured her ankle, with Bailey insisting that she get x-rayed as she couldn't treat her properly until she found out what was wrong. That is when they found out about she was osteoporotic - and the doctors were concerned as to why she had it so young. Ruthie admitted that she had lost 40 pounds to try and meet her boyfriend's conditions so they could live together, and Bailey insisted she would have to make lifestyle changes so she would heal properly. But as the doctors were explaining her surgery to her, Ruthie started to vomit blood from an ulcer - and once they reached the operating room, they were unable to save her,

Ken Marino

The Veronica Mars alumni played restaurant manager Brad Ackles, who got injured when a disgruntled former employee named Petey came back to their workplace with a gun. 14 employees were injured in the incident, and two were killed, but Brad got out of the way by diving through a window. He had a number of lacerations from the shattered glass. Izzie ends up treating and bandaging him up. But when Brad goes to leave the hospital, it is revealed that Petey has returned - and the restaurant manager is shot and killed.

Mandy Moore

Before she was mothering the Big Three on This Is Us, the actress played Mary Portman in what - let's face it - was probably one of the most dramatic episodes in the history of Grey's. Mary was a patient at Seattle Grace Mercy West when Gary Clark stormed the hospital with the intention to kill Derek Shepherd, Richard Webber and Lexie Grey in revenge for the death of his wife, who was also a former patient. Mary first appeared in season six of the medical drama, but returned the following season for a surgical procedure. She passed away after slipping into a coma.

Laurie Metcalf

In season two, Lady Bird star Laurie Metcalf played Beatrice Carver, a mum who had been diagnosed with terminal cancer - and had yet to tell her daughter she was sick. Once the Seattle Grace doctors gave her her diagnosis, she told them to do whatever they could to give her as much time as possible - only for her to be told that any further surgery will be too much stress on her body. Beatrice tried to leave the hospital against medical advice since her daughter's birthday was the next day and she didn't want them to celebrate it in hospital, but Alex convinced her to stay. She eventually told her daughter the truth and gave her all the advice she would have given over the years.

Leslie Odom Jr

Hamilton's Leslie Odom Jr played P.J. Walling, one of the patients who was undergoing a domino kidney transplant in season five. P.J.'s father, Kurt, was almost among the patients involved in the transplant - and had offered him $10,000 to participate in the procedure. After his surgery, P.J. was mostly thinking of just taking the money and leaving the hospital, but when his dad suffered a seizure and delayed graft function after the surgery, he decided to stay by his dad's side.

Demi Lovato

The former Disney star featured in season six of the medical drama as Hayley May in a season six episode. Her teenage character had been diagnosed as a paranoid schizophrenic - and her parents had decided to her have her committed to a psych ward. Alex and Lexie eventually discover that she actually had Superior Canal Dehiscence syndrome, which was an opening in a bone in her ear that was skewing her perception of the world around her.