… And Jim Backus was in that episode too. Cool! 
I love Jill Townsend. She played “Dulcey” in Cimarron Strip and was “Elizabeth” in the original Poldark series.
Right at the end of the movie What’s Up,Doc (about 1 minute into this):
In The Good Place, there was this scene in the finale of season 2.
Similarly, in an episode of Green Acres, Lisa and Oliver go to Washington to see their Senator. The following exchange occurs:
Lisa Douglas: [recognizes senator from the late, late show] Ohhh, you must be the fellow who was in Death Valley Days!
Oliver Wendell Douglas: No, that was Ronald Reagan.
Lisa Douglas: Who?
Senator Talbot: Ronald Regan. He’s the governor of California.
Lisa Douglas: Well then, which movie star are you?
Senator Talbot: [smugly, as a star] Lyle Talbot!
Lisa Douglas: Oh. I guess I never saw you.
Of course, the part is played by Lyle Talbot.
Mark Hamill in What We Do In the Shadows.
There was an episode of Hot in Cleveland, where Valerie Bertinelli’s character finds herself at a 12-step meeting of some kind or another, and someone says to her to take it “one day at at time.” She gets an odd look on her face, as though she’s trying to remember where she’s heard that before. She had to hold it for a long time, because the audience was laughing pretty hard.
In 1936, Buster Crabbe starred in the matinee serial Flash Gordon.
In 1939, Buster Crabbe starred in the matinee serial Buck Rogers.
In 1979, he made a guest appearance in the TV series Buck Rogers in the 25th Century,
playing “Brigadier Gordon”.
“Where did you learn to shoot like that?”
“I’ve been doing this since before you were born, Captain.”
“You think so?”
“Young man, I know so.”
Chyler Leigh had a rather varied career before she joined Supergirl in the role of Alex Danvers and the writers liked to incorporate her past roles into her character’s backstory. Ales had a a “strange goth phase”, referring to Chyler’s appearance in a Marilyn Manson video. Alex had also been a doctor in Seattle, as Chyler was previously a series regular in Grey’s Anatomy.
The Incredibles included a reference to Jason Lee’s earlier character in Mallrats.
Martin and Charlie Sheen clearly aren’t afraid to send up previous roles.
A side note, but that was also John Cleese’s character’s name in A Fish Called Wanda.
This short animation is filled with references to Mark Hamill’s career.
In Mallrats Ethan Suplee calls Shannon Dougherty Brenda. She gets upset and I’ve never been sure that she is acting.
There was this fun post-credits scene for Jennifer Aniston in We’re The Millers:
Well, what about that episode of Hot in Cleveland featuring guest appearances of old friends of the Betty White character played by Valerie Harper and Cloris Leachman, in which someone said that the character played by Mary Tyler Moore would be unable to join them, but they walk into the restaurant to see her already sitting at the table and Betty White says “Looks like she made it after all.”
In Futurama the main character Philip J. Fry meets a robot named Billy West and says “What a stupid fake name!!”
Billy West is the name of the voice actor for Philip J. Fry as well as other characters on the show.
Mark Hamill playing The Trickster on the TV show Flash
Axel - I am your father.
On St Elsewhere, Betty White playing a US Navy officer was mistaken for “Sue Ann Nivens, the Happy Homemaker” by a mental patient who thought he was “Mary Richards.” (He threw his hat in the air at the end of that episode, too.)
Oh, yes, and of course Cocknocker from Jay & Silent Bob Strike Back, in which Mark Hamill’s oversized fist is sliced off, prompting him to say “Not again!”
Frakes’s character on TNG was often addressed (by Picard, anyway) as “Number One.” In that clip, he tells Castle, “I’m your number one fan.”
Scott Bakula was on Always Sunny and they refed Quantum Leap. It was kinda funny, I guess.
This would have been even better if the two Chinese guys looked at each other in complete confusion, or if one had said, “What the hell is he saying?”
Firefly’s actors notoriously mangled their Mandarin lines.