1. Demi Lovato, Season 6 Episode 22 ("Shiny Happy People")

Demi Lovato, ex-Disney Channel star and pop sensation, played Hayley, a 16 year old diagnosed with schizophrenia after talking to multiple doctors. After landing in Seattle Grace and attempting to stick a needle in her chest, the other doctors believed the diagnosis, all except Alex Karev. After restraining her, Dr. Karev urged the other doctors to let him do more tests, but with some help with Lexi Grey (RIP), he found her diagnosis to be Superior Canal Dehiscence Syndrome, which took away her ability to hear the organs inside of her.

2. Millie Bobby Brown, Season 11 Episode 15 ("I Feel The Earth Move").

Millie's roles have always been "bitchin'," even before "Stranger Things." Brown played 11-year-old Ruby, who witnessed her mother collapsing and losing consciousness and the ability to breathe after an Earthquake struck them. After not being able to get through with 911, she directly called the hospital for help. Through the phone, the doctors guided her through the Heimlich and chest compressions to the speed of "Stayin' Alive." After the phone died they were desperately waiting for Ruby and her mom to arrive, which they did, and her mother made a full recovery.

3. Sarah Chalke, Season 9 Episode 19 ("Can't Fight This Feeling").

After her character Stella left Ted at the alter in "How I Met Your Mother," Sarah Chalke guest starred as single mother Casey, whose son was diagnosed with strep throat, but urges Dr. Wilson to do additional tests, as she does not think it's strep. After emotions run high and Sarah requests a second opinion, Dr. Grey, reluctant, does more tests for some of the diseases she found online that match his symptoms. After they all come back negative she does one final strep test, it comes back negative, and she checks for red eyes. After confirmation of red eyes, she realizes Casey's son has a disease she found online, Kawasaki disease, which if not treated within the first 10 days of a fever starting could give permanent heart damage. They luckily were there on the 10th day of the fever and Dr. Grey was able to prevent that. Fun fact about this episode—Sarah Chalke's child has this disease! (Well, not fun for Sarah and her family, but you get the point)

4. Seth Green, Season 4, Episodes 9 and 10 ("Crash Into Me, Part 1 and 2").

Seth Green, voice actor from iconic shows like "Family Guy," "Robot Chicken" and "Phineas and Ferb," taught us that laughter isn't always the best medicine; sometimes it might kill you, oops. Seth played Nick, who came in to get a tumor removed near his carotid, which carries blood to the neck and head. They were able to get a good chunk of it out, but there was concern that it didn't leave a lot of skin to cover the carotid artery, which gave a big risk of rupture. Unfortunately, after an artery burst after joking around and laughing with Lexie Grey, he started bleeding out, eventually had a stroke and was pronounced dead.

5. Dylan Minette, Season 4 Episode 5 ("Haunt You Every Day").

Before Dylan played Clay in the Netflix series "13 Reasons Why," he played young patient Ryan who was born with no external ears, which limited his ability to hear. He went to the hospital to find Mark Sloan, gifted plastic surgeon, to ask him if he could build him new ears and perform the surgery for free. After agreeing, Ryan solicited Meredith's help in finding other nurses and doctors to donate their time to this surgery and was successful. Fans say that his character on "13 Reasons Why" could possibly be connected with his character on "Grey's Anatomy," and I dig it.

6. Abigail Breslin, Season 3 Episode 3 ("Sometimes a Fantasy").

Abigail Breslin, known best for her roles in "Little Miss Sunshine," "Scream Queens" and "My Sister's Keeper," played a young foster girl named Megan who cut her leg open on the playground. The doctors were susceptible that her foster parents were abusing her because of a DIY stapling job that was found on a different cut on her leg, but she assured them she stapled her wound together herself to avoid another hospital visit. After seeing this they realized she has no pain sensitivity, and after proving this theory with no pain from her side, they realized she had a rare disease called congenital insensitivity to pain with anhidrosis, or CIPA, that gives her the ability to not feel pain. Because of this, someone with this disease could get hurt and not realize, which leaves injuries and illnesses undiagnosed, so they sent her into surgery to fix this.