Other mistake: At the Circle K when future Bill and Ted have finished talking to present Bill and Ted and go back into the phone booth, where are the other 5 historical figures? Especially as it is emphasized that they are all squished together, when they land you can see Beethoven, but he isn't there at the end when they leave.
Abraham Lincoln: Fourscore and...[looks at his pocket watch]...seven minutes ago... We, your forefathers, were brought forth upon a most excellent adventure conceived by our new friends, Bill...and Ted. These two great gentlemen are dedicated to a proposition which was true in my time, just as it's true today. Be excellent to each other. And... Party on, dudes!
Bill: Ted, while I agree that, in time, our band will be most triumphant, the truth is, Wyld Stallyns will never be a super band until we have Eddie Van Halen on guitar.
Ted: Yes, Bill. But, I do not believe we will get Eddie Van Halen until we have a triumphant video.
Bill: Ted, it's pointless to have a triumphant video before we even have decent instruments.
Ted: Well, how can we have decent instruments when we don't really even know how to play?
Bill: That is why we NEED Eddie Van Halen.
Ted: And THAT is why we need a triumphant video.