Beavis and Butt-Head
In "The Butt-head Experience" episode (June 7, 1993) of animated tv series Beavis and Butt-Head, Butt-head falls asleep at work and dreams that the eponymous MTV metalhead idiot teens of are big rock stars performing on stage, but he doesn't even bother to fantasize them having any musical talent.
The Beavis and Butt-head Experience CD (1993) starts with a similar fantasy sequence.
In the "Garage Band" episode (August 1, 1997), Beavis and Butt-Head try to form their own band and tell a venue that they are Metallica. Then they give up and go home.