Alex Winter claimed that he gets two types of letters from teachers; positive ones from history teachers for encouraging students to learn about history, and negative ones from English teachers for affecting the way students speak.
The phone booth time machine was given away as a contest prize by Nintendo Power magazine, which was promoting Bill & Ted's Excellent Video Game Adventure (1991).
In the original script, the time machine was a 1969 Chevy van. The filmmakers thought that was too similar to Retour vers le futur (1985), so they changed it to a phone booth (and were reportedly unaware that Docteur Who (1963) uses a police telephone box as a time machine).
In the film, Bill and Ted claim that they need Edward Van Halen in their band to make it better. After the film was released, he jokingly said he would have joined their band if they had asked.