These are interesting sub-cases of the subject where the actors are playing themselves as characters in shows. Obviously you could catch any actor on a talk show where they refer to their previous roles, but in these cases they have actual roles in a show, these are lines and part of the dialogue.
They also weren’t exactly playing themselves, but rather a parody version of themselves. So “Jennifer Grey” in the show was not actually Jennifer Grey the actress.
And Mel Torme wasn’t the real Mel Torme on Night Court. But I don’t think that meets the spirit or letter of the law with this OP.
That is not Mel Torme.
No, it isn’t.
It’s Wil Wheaton.
Sure it wasn’t Michael Dorn?
Shhh, that’s top secret.
The Rocky and Bullwinkle movie had Robert De Niro parodying his scene from Taxi Driver.
In one episode of St. Elsewhere a guy suffering from amnesia is desperately searching for an identity. He finally decides he is Mary Tyler Moore. the hospital is visited by someone from the Surgeon General’s office, and he joyfully greets her “Sue Ann!” Said rep is played by Betty White.
In the same show, Dr. Mark Craig, played by William Daniels, badly injures his hand in a stupid fasxhion. He and his wife travel to Philadelphia to visit a surgeon who specializes in healing hand injuries. As they are walking outside his wife complains to him “Mark, why did we have to come to Philadelphia in the summer? It’s too damned hot!” And Dr. Craig starts singing “It’s hot as hell, in Philadel-phia!” A reference to the musical 1776, in which he starred as John Adams.
On Night Court, they had a little old lady visit the court who couldn’t tell TV from reality - she thought her husband had been falsely imprisoned (it was a character from a soap opera she was talking about). She talked about all the friends she had - and all of them were tv characters. One of them was “The Fonz” - and of course, the little old lady was played by Marion Ross, of “Happy Days”
Further referred to in a Bob Newhart Show reunion, where Bob kept talking about a weird dream he had about running an inn in Vermont. At the end, Larry, Darryl, and Darryl show up on the elevator.
I note that Newhart’s George and Leo had "The Cameo Episode,’ where actors from The Bob Newhart, Newhart and Taxi (Judd Hirsch was Newhart’s co-star) showed up. George (Newhart) ended up in a group therapy session while Leo (Hirsh) ended up driving a taxi.
Alan Hale also appeared in an episode, referring to Denver as “Little Buddy.”
The Drew Carey Show had Marion Ross as Drew’s mother and June Lockhart playing Lewis’s mother. One scene had them watching a TV show. Drew’s mother (Marion Ross) says, “Oh look. It’s that show with the collie.” (apparently Lassie) Lewis’s mother (Lockhart) says, "If you ask me, the mother was the star of the show. Ross replies, “Oh no, it was the dog.”
Another episode had Drew in love with an older woman (Shirley Jones of the Partridge family). Danny Bonaduce played her obnoxious adult son.
Someone earlier mentioned Supernatural. Here is when the mention of Gilmore Girls struck fear into Sam.
Dean Winchester is not happy to find out Jensen Ackles was in a soap opera.
Negan’s bat Lucille makes an appearance on Supernatural. Jeffery Dean Morgan played their father.
Brandon Routh, who has played Superman in multiple productions, starred in the tv series “Partners”, playing the gay boyfriend of Michael Urie’s character, Louis McManus. Louis is trying to get him to try on some glasses that would make him look cool. Routh’s character says that he doesn’t like wearing glasses, but he puts them on to humor him. Louis says, “Wow, you look like a totally different person.” And Routh says, “Told you so, Lois. … I mean, Louis.”
In another episode, Louis brags about sleeping with “this big, gay superhero.”
In last year’s Crisis on Infinite Earth’s, Routh met a Superman from another Earth. Routh played both roles, a reference to his role in Superman Returns
Also, in the first Arrowvese crossover, Routh’s character, Ray Palmer, aka the Atom, is introduced to Kara Danvers, aka Supergirl. Palmer remarks, “She looks like my cousin.” Of course, Kara and Kal-El are cousins.
In season 3 of Legends of Tomorrow the Big Bad was the demon Mallus. He was CGI but voice acted by John Noble. The Legends realize he sounds a lot like the actor John Noble and hatch a scheme that involves Mallus saying things that they need him to say. Since there is a time machine readily available they travel back in time to New Zealand while he is filming Lord of the Rings and trick John Noble to read the lines they want Mallus to read instead of John Noble acting as Mallus. Now I’m confused but it works. The episode was titled “Guest Starring John Noble.”
