Timothy Bottoms played George W. Bush in the Parker/Stone Comedy Central spoof “That’s My Bush,” and then did a serious portrayal of him in the made-for-cable movie “D.C. 9/11.”
Howard da Silva, having created the role of Benjamin Franklin on Broadway in 1776, went on to play him in the movie version. He also did a series of commercials for GE as the character.
Hugo Weaving is currently playing an unnamed character who is obviously Agent Smith from the Matrix movies on a commercial for GE. (I like the coda, which doesn’t always air, where he offers a kid a pair of lollipops. “Red or Blue?”)
George Lazenby, having played James Bond only once in On Her Majesty’s Secret Service, went on to play an unnamed British Agent who drives an Aston Martin with “007” plates in the TV movie The Return of the Man from Uncle
Similarly, Roger Moore seemed to play a version of James Bond in The Cannonball Run, driving an Aston Martin with the license plate “6633 PP”, the same as in two Bond films.
There are countless examples of actors who have reprised their roles for video games based on their movies, and countless actors who have repeated their Broadway roles for movies (and, occasionally, repeated their movie roles for Broadway, as with Julie Andrews in Victor, Victoria)
As did Sharon Stone (from Basic Instinct), and Bogart (from Maltese Falcon, I think - but that was a digital inlay.)
(I’ve always hated that they “fixed” the dialogue on Bogart’s scene. In the original, the desk sergeant says, “Jones, you’re with the black-and-white” as the B+W Bogart saunters up. In everything from the DVD release forward, the line is extended to “…you’re with the black-and-white avatar(?) of Humphrey Bogart.” Like, we were too stupid to get the joke or sumpin’.)
In reverse, Irene Ryan had a cameo as “Granny,” driving a truck very similar to the Clampetts’ truck in the movie “Don’t Worry, We’ll Think of a Title.”
He also played W. in Crocodile Hunter: Collision Course.
He also did some in-character PSAs for the U.S. Postal Service.
Connie Britton played the coach’s wife in the decent 2004 film Friday Night Lights. She then went on to play the coach’s wife (different character name, different actor playing the coach, who had a different character name) in the brilliant TV series Friday Night Lights.
We have a winner. That’s awesome.
John Houseman played snooty law professor Charles Kingsfield in the movie and TV versions of The Paper Chase.
He also made guest appearances as Kingsfield on the sitcoms ***The Associates ***and 227.
Ron Moody played Fagin in the movie version of Oliver! in 1968- decades later, he played Fagin in the Broadway revival of the musical.
The TV series Alice Was based on the film Alice Doesn’t Live Here Anymore. The only actor who played the same role was Vic Tayback as Mel.
I vaguely remember an episode of some TV show that featured a bunch of cameos in a group therapy session for henchmen. One of them was Richard Kiel ostensibly playing Jaws but I can’t find any such listing on IMDb.
If we start in on SNL, we could be here a long while.
Matthew McConaughey reprised his role as David Wooderson from the movie Dazed And Confused for the music video of the song “Synthesizers” by Butch Walker and The Black Widows.
One noteworthy episode in which Will Ferrell returned as a guest: while the musical guest (Queens of the Stone Age) was playing, Ferrell joined in with his cowbell.
Mark Metcalf, who played Doug Niedermeyer in Animal House, reprised the role for the Twister Sister video “We’re Not Gonna Take It.”
Not quite what the OP is looking for, but the character John Falstaff has a fairly minor role in Shakespeare’s Henry IV histories. He was so popular, Shakespeare made a comedy (The Merry Wives of Windsor) with Falstaff having a major role.
They also appeared in the 1958 Lone Ranger feature film based on the TV series.
Harpo also stayed in character throughout his appearance on I Love Lucy.
Apparently I was thinking of the first Inspector Gadget movie so never mind.