The future "Black Panther" shares the screen with Carl Weathers in a Season 15 episode, playing a young boxer who comes into the ER after taking a beating in the ring.
Chadwick Boseman —
The future "Black Panther" shares the screen with Carl Weathers in a Season 15 episode, playing a young boxer who comes into the ER after taking a beating in the ring.
Warner Bros. Television/Hulu
Before he was baddie Negan on "The Walking Dead," Morgan played a firefighter who needs the help of ER docs in the field after he gets trapped underneath a turned over train in the show's 150th episode.
Jeffrey Dean Morgan —
Before he was baddie Negan on "The Walking Dead," Morgan played a firefighter who needs the help of ER docs in the field after he gets trapped underneath a turned over train in the show's 150th episode.
Warner Bros. Television/Hulu
The future voice of Olaf from "Frozen" guest stars in Season 11's "Here and There" as a man serving with Dr. Gallant in Iraq.
Josh Gad —
The future voice of Olaf from "Frozen" guest stars in Season 11's "Here and There" as a man serving with Dr. Gallant in Iraq.
Warner Bros. Television/Hulu
The Oscar-winning actress plays a patient named Maria Jones, a pregnant woman who has severe abdominal pain, in Season 5's "Hazed and Confused."
Octavia Spencer —
The Oscar-winning actress plays a patient named Maria Jones, a pregnant woman who has severe abdominal pain, in Season 5's "Hazed and Confused."
Warner Bros. Television/Hulu
Park plays a man with developmental delays whose teenage sister has a baby in the ER in a Season 11 episode.
Randall Park —
Park plays a man with developmental delays whose teenage sister has a baby in the ER in a Season 11 episode.
Warner Bros. Television/Hulu
The Oscar nominee appears in Season 10's "Forgive and Forget" as a woman who takes care of her sick father.
Jessica Chastain —
The Oscar nominee appears in Season 10's "Forgive and Forget" as a woman who takes care of her sick father.
Warner Bros. Television/Hulu
Nash has a brief role in Deason 10's "Missing" as a mom who believes her missing daughter was brought into the ER as a Jane Doe.
Niecy Nash —
Nash has a brief role in Deason 10's "Missing" as a mom who believes her missing daughter was brought into the ER as a Jane Doe.
Warner Bros. Television/Hulu
Henson is one of a few actors who show up more than once as a guest star during "ER"'s 15-season run. She made her first appearance as a family member of Dr. Peter Benton in Season 4 ("Of Past Regret and Future Fear"). She was brought back episodes later to play a different character.
Taraji P. Henson —
Henson is one of a few actors who show up more than once as a guest star during "ER"'s 15-season run. She made her first appearance as a family member of Dr. Peter Benton in Season 4 ("Of Past Regret and Future Fear"). She was brought back episodes later to play a different character.
Warner Bros. Television/Hulu
The future "American Horror Story" star played one of two Amish teens who are involved in a car accident in Season 10.
Finn Wittrock —
The future "American Horror Story" star played one of two Amish teens who are involved in a car accident in Season 10.
Warner Bros. Television/Hulu
Offerman shows up in a Season 4 documentary-style episode ("Ambush") and plays a man whose friend comes in under respiratory distress.
Nick Offerman —
Offerman shows up in a Season 4 documentary-style episode ("Ambush") and plays a man whose friend comes in under respiratory distress.
Warner Bros. Television/Hulu
The future Luke Cage has a blink-and-you'll- miss-it appearance as a paramedic who treats an ER intern after an accident in Season 9.
Mike Colter —
The future Luke Cage has a blink-and-you'll- miss-it appearance as a paramedic who treats an ER intern after an accident in Season 9.
Warner Bros. Television/Hulu
The "Parks and Recretion" actor comes into the ER in a Season 1 episode ("Full Moon, Saturday Night") after being hit by a car.
Adam Scott —
The "Parks and Recretion" actor comes into the ER in a Season 1 episode ("Full Moon, Saturday Night") after being hit by a car.
Warner Bros. Television/Hulu
The comedian appears (with hair!) as a member of Dr. Benton's legal team in a Season 8 episode called "Quo Vadis?"
Keegan-Michael Key —
The comedian appears (with hair!) as a member of Dr. Benton's legal team in a Season 8 episode called "Quo Vadis?"
Warner Bros. Television/Hulu
The "Mad Men" actor plays a troubled artist who comes into the ER after eating half a tube of paint in Season 6's "Truth and Consequences."
Vincent Kartheiser —
The "Mad Men" actor plays a troubled artist who comes into the ER after eating half a tube of paint in Season 6's "Truth and Consequences."
Warner Bros. Television/Hulu
Penn guest stars as a doctor in another hospital who treats Dr. Benton's young son after an auto accident in Season 8's "The Longer You Stay."
Kal Penn —
Penn guest stars as a doctor in another hospital who treats Dr. Benton's young son after an auto accident in Season 8's "The Longer You Stay."
Warner Bros. Television/Hulu
The "Breaking Bad" actor helps Dr. Greene diffuse a bomb in Season 5's "They Treat Horses, Don't They?"
Dean Norris —
The "Breaking Bad" actor helps Dr. Greene diffuse a bomb in Season 5's "They Treat Horses, Don't They?"
Warner Bros. Television/Hulu