Pretty sure his character worked there–I think we see him sweeping the floor at one point. Wikipedia and other sources describe his character as “Fred the bartender.”
Worth noting, though, that at the name, basically nobody was familiar with the name Victoria Vetri, as the actress’s stage name for many years was “Angela Dorian.”
I came in to mention this one.
Not meta-casting but rather, meta-costuming: L. Frank Baum’s coat finding its way into The Wizard of Oz.
Similarly, when the recent Dark Shadows movie needed someone to play a 1970s era Alice Cooper, they cast the 2010s era Alice Cooper.
I think they did that as often as they could. Ted Nugent also appeared as himself (he invites Donna back to his hotel room but she turns him down). Also in the first season the cast (or somebody) sang the theme song which was meant to ‘sound like Cheap Trick’. Sure enough, in season two & beyond they had the real band singing it!
I don’t think Chuck Yeager’s character is ever seen bartending, he’s just kinda hanging out there. He has one small speaking scene:
He approaches Jeff Goldblum & Harry Shearer and asks, “You fellas want a drink of whiskey?” to which Shearer replies, “I’d like a Coca-Cola”, to which Yeager confusedly replies, “A Coke?!?” and Shearer nods and says, “In a clean glass”.
A contest to win a cameo role on How I Met Your Mother was won by Conan O’Brien. Given his fame, the writers wanted to give him a larger speaking role, but he insisted on just taking the non-talking extra spot he’d won. So in one episode, you can see him hanging out in the back of the bar while the main characters do their usual thing.
In the second season episode of South Park, Big Gay Al’s Big Gay Boat Ride, the part of Stan’s gay dog Sparky was played by George Clooney. All he did was make barking sounds, he had no actual lines! Parker & Stone just thought it would be so funny to have this Hollywood A-lister in the studio just to make dog sounds (and Clooney was an old friend of theirs). When they did their first Thanksgiving episode they asked Jerry Seinfeld to play the turkey (Goobles). But when he found out it would be just him making silly turkey noises he declined.
Fred (Yeager) also brings Scott Crossfield’s steak dinner to celebrate his flight at mach 2, and says “here you go, Scotty, compliment’s of Pancho’s.” So it certainly sounds like he works there.
Two fairly well-known examples that come to mind:
In The French Connection (1971), Gene Hackman and Roy Scheider play characters based on NYPD detectives Eddie Egan and Sonny Grosso. Both Egan and Grosso appear in the movie, Egan as Hackman and Scheider’s supervisor.
In the 2005 Steven Spielberg remake of War of the Worlds the grandparents of the Tom Cruise character’s son and daughter are played by Gene Barry and Anne Robinson, who played the starring roles in the 1953 version.
Speaking of The Right Stuff, what I like about the casting is that Ed Harris is John Glenn, Scott Glenn is Alan Shepard, Sam Shepard is Chuck Yeager, and Chuck Yeager is the bartender (or Fred some guy who hangs out at the bar and vaguely seems to work there).
and Fred Ward plays Gus Grissom. 
Yes, and Colin Firth accepted the Bridget Jones role as a sort of a way to mess with the memory of the original Mr Darcy role, which I remember reading he isn’t all that fond of nowadays.
As for the other thing, the second Bridget book has her getting a job as a reporter and getting to interview Colin Firth (or better said ask him about the wet shirt scene, as that was what she was the most interested in ). So when the time came for the second movie to be made there was this conundrum to be solved, as they couldn’t cast Colin Firth as himself (or anyone looking like him) because he was already in the movie as Mark Darcy
Gus? An astronaut named “Gus”?
And Jane Dornacker, who would later die reporting traffic in a helicopter, plays the stern, nerdy-looking nurse.
“What’s your middle name?”
“Ivan” *(At the height of the Cold War remember)
*
“Maybe Gus isn’t so bad…”
Holy flurking schnit! I had no idea that was her…
Yeah, he’s a bartender. He’s clearly seen working behind the bar when Glennis Yeager comes in during the Scott Crossfield celebration scene. Just saw it a few minutes ago.
A couple of author cameos: James Dickey played a sheriff in Deliverance and John Irving played a referee in The World According to Garp.
There seems to be just two cases where a significant author plays the main character in the film of his novel - Richard Wright in Native Son and Mickey Spillane in The Girl Hunters.
And a stationmaster in The Cider House Rules.