50 famous actors you probably forgot were on Grey's Anatomy

After accidentally running over her husband and bringing him to the hospital, a pregnant Jen (also the character's name) collapsed and later had a seizure due to an aneurysm. She went into surgery, during which she was given a blood transfusion that put her pregnancy at serious risk. Ultimately, she died and the baby lived. (Season 5.)

The House Of Cards and Entourage actress played Dr. Cahill, a physician brought in to make the hospital run more efficiently. (Season 9.)

She played a paramedic who had to keep her hand on a wound lest she detonate a bomb that was inside the patient. Yes, really. (Season 2.)

As Beth Monroe, she came to the hospital with an inoperable tumor and was the first patient to survive Derek and Meredith's clinical trial. Her boyfriend, Jeremy, was also part of the trial; he died. (Season 4.)

He was the head of the bomb squad and died trying to carry the bomb out of the hospital. (Season 2.)

The Little Miss Sunshine and Scream Queens star played a little girl who was immune to feeling any pain. (Season 3.)

The Mad Men and Handmaid's Tale star played an overprotective and slightly unhinged daughter, whose mother suffered from a condition that caused bone to grow at the sight of an injury. The mum died in surgery. (Season 3.)

The Breaking Bad star played Jake Burton, a young man with craniodiaphyseal dysplasia. The bone disorder, "lionitus," causes calcium to build up in the skull, leading to facial disfiguration. In Jake's case, the growth moved inward as well, and Derek was tasked with removing the resulting brain tumour. Jake died in surgery. (Season 2.)

Friday Night Lights star Zach played a lieutenant in the U.S. Army who came to the hospital with terrible leg pain, asking for an amputation. Even though she could find nothing wrong with the leg, Callie Torres agreed to perform the surgery so he could return to active duty. (Season 5.)

The Scrubs actress played the mother of a sick boy who Jo Wilson wrongly diagnosed with strep throat. The kid in fact had a rare heart condition, Kawasaki disease, which Jo caught just in time to prevent permanent damage — mostly thanks to the boy's persistent mum. (Season 9.)

She played Nikki, a woman who fell out of a tree, where she was stationed to spy on her ex-boyfriend, then refused to have surgery due to superstitions. She died. (Season 2.)

She played a blood donor in the show's seventh season and went on to have a much bigger role in the Shondaverse, as Quinn on Scandal.

The Transparent star plays Donna Gibson, a trans woman who was diagnosed with breast cancer. (Season 3.)

Ken played Brad, a man who literally dodged a bullet when a disgruntled ex-employee, Petey, showed up to Brad's restaurant with a gun. Brad was leaving the hospital when Petey appeared again — and this time killed him. (Season 2.)

The Sons Of Anarchy star played Ruthie, a woman with severe osteoporosis caused by malnutrition. (She'd lost 40 pounds to meet her boyfriend's criteria for moving in together.) She died after vomiting up blood due to a bleeding ulcer. (Season 4.)

The Buffy and Gilmore Girls star (and TV and movie writer) played Paul, a guy who thought he was meeting his girlfriend's cat — and it turned out that her cat was a lion. (Season 8.)

Before becoming a Broadway god as Aaron Burr in Hamilton, Leslie played a young man who begrudgingly agreed to donate a kidney to his father. (Season 5.)

The Mad Men star played a driving instructor who saved his girlfriend's son's life by getting him to the hospital in time. (Season 12.)