I saw a Beverly Hillbillies episode recently with a guest appearance by Lester Flatt and Earl Scruggs (who also performed the show’s iconic theme song, for those who might not have known).
The premise was that Flatt & Scruggs were old friends of Jed Clampett back in the hills, and paid a visit to his new home. While there, Lester turned to Earl and said, “Let’s play Jed that song we wrote about him!” And they commenced to playing and singing the Beverly Hillbillies theme song right there in front of the show’s characters! I found it a kind of weird, fourth-wall breaking sort of moment.
Can anyone think of another instance of something like this happening on a TV show? The Friends never went to a Rembrandts concert to hear them play “I’ll Be There For You.” The Brady kids, even after they became a singing group, never broke into a chorus of “Here’s the story, of a lovey lady…” during an episode.
A movie rather than a TV show, but in The Incredibles, Mr. Incredible hums the main theme of the movie while he’s walking into his kitchen after a late night of heroism.
Also, various of the Marvel movies have referenced the TV theme songs for their respective movies–a lady is playing the Spiderman theme song in the first movie with Tobey McGuire, Rhodey’s ringtone for Tony Stark is the Iron Man tv show theme, etc.
Once the cast of How I Met Your Mother pretended that they were a band, and the song they played was their theme (actually, I think that occurred in Barney’s imagination, but still).
Boston Legal featured several performances of the theme, once on a kazoo, and once hummed by Jerry.
Apparently the theme to Weeds, Little Boxes, is referenced in one episode when Nancy tells Shane that he’s going to “…become a doctor or a lawyer or a business executive.”
The anime Sailor Moon has the characters sing or hum the “Moonlight Densetsu” constantly which is a fun in-joke until you realize Usagi’s locket which is thousands of years old also plays the song making it seem the song is actually some extremely old folk song.
The movie version of MASH includes the theme song for the TV show, Suicide is Painless. The lyrics are included in the movie, but not the TV theme. I don’t recall if the song was used as the theme song for the movie.
Ricky Ricardo sang the I Love Lucy theme to Lucy in one of the episodes. I believe it was the one where there was a giant misunderstanding and they made up in the end.
It’s not a TV show, but in the James Bond film On Her Majesty’s Secret Service a janitor sweeping up in Draco’s offices is whistling the theme from Goldfinger