How about Songwriter, where Kris Kristofferson’s real backing band backed up Lesley Anne Warren, while Willie Nelson’s real backing band backed up Kris?
In Human Highway (1982), co-directed by Neil Young, the group Devo perform several numbers, but not as themselves. Neil Young performs as a non-Neil Young character.
The Standells, best known for “Dirty Water,” appeared in several movies and TV shows- sometimes as themselves, sometimes playing fictitious bands with mother names.
Steel Dragon was a fictional band in Rock Star but was composed of actual rock musicians, including Zakk Wylde and Jason Bonham.
The Donnas appeared in Drive Me Crazy (as The Electrocutes). They’d released three albums and I’d heard of them by the time that film came out so I guess that could count as famous.
Sha Na Na played Johnny Casino and the Gamblers in Grease.
Well, they weren’t well known. But The Wellingtons appeared as a rock group called “The Mosquitoes” on Gilligan’s Island.
British rock band Slade appeared in the 1975 film Slade in Flame portraying the rise and fall of the fictional band Flame.
TCMF-2L
Chad and Jeremy appeared in The Dick Van Dyck Show as “The Redcoats,” a fictitious band (though they did do a shout out, thanking their friends Chad and Jeremy).
Damn, that was the the one I was going to post! Here they are playing David Bowie’s “Fame” in the movie.
The Nitty Gritty Dirt Band appeared in the movie Paint Your Wagon as a nameless band playing the piece Hand Me Down That Can o’ Beans.
They were also on “Batman.”
Not a band, but crooner Al Martino played the fictional singer Johnny Fontane in The Godfather.
The band Lustra was “Donny’s Band” in the movie EuroTrip, performing Scotty Doesn’t Know. Donny was played by Matt Damon, who lip-synced the song.
On an episode of “F Troop,” a mop topped English band called the Bedbugs appears.
Their guitarist and lead singer was Lowell George, and their drummer was Richie Hayward. Together, they were the founders of Little Feat.
Bauhaus, the Hunger (1983), with David Bowie in a non-musical role.
Oingo Boingo was in Back to School.
Since they had a giant neon sign behind them that said “Oingo Boingo” I don’t think they were playing a fictional band.
Oingo Boingo are credited as themselves in Back to School.
In the Dick Van Dyke episode called “The Redcoats are Coming” the Redcoats are played by Chad and Jeremy.
The OP stipulates “band” … so I may assume that instances such as the following are not in play?
[ul]
[li] Joan Jett as Patti Resnick in Light of Day[/li][li]Bette Midler as Mary Rose Foster in The Rose[/li][li]Neil Diamond as Jess Robin in The Jazz Singer[/li][li]Paul Simon as Jonah Levin in One Trick Pony[/li][/ul]