Bill & Ted's Excellent Adventure (1989)

Bill (Alex Winter) and Ted (Keanu Reeves) have spent so much time forming their rock band that they’re flunking history. Ted’s dad threatens to send him to military school if he doesn’t pass. Luckily, Rufus (George Carlin), a guardian angel from the future, has a time-traveling phone booth to take them into the past to learn about the world. Their journey through time turns out to be a blast…but will they learn enough to pass their class and keep their rock band together?