The film's loaded with cameos that all make a huge comic impression because of the great actors Reiner chose for them. Bruno Kirby plays the limo driver taking the boys to a gig. He's a Sinatra buff, who tries to explain Sinatra's appeal to the band before they roll up the limo window to shut him up. But doesn't the band also have an effect on their audience like Sinatra, asks Marty?
DRIVER: But it's...it's a passing thing...it's uh.... I mean I would never tell them this but this is uh...this is a fad.