Other mistake: Just before the evil robots capture Bill and Ted's girlfriends, after they crash through the window, the girlfriends ask the robots: "Who are you?" and Bill goes "Well, I'm really Evil Ted!" and unzips himself and out pops Evil Ted, and the other robot goes, "And I'm really Evil Bill!" and out pops Evil Bill. When the robots are herding the girlfriends out just before knocking them out with their breath, you can see two sets of clothes in the bottom left corner if you watch closely.