Continuity: At one point, Bill is on the left inside the phone booth and Ted is on the right. When the camera switches away, then back, they've changed sides. I think it's right before they meet their future selves.

Revealing: At the end, when all the historical figures are going back into the phone both, you can see the trap door in the back open and the people go through it. It would be kind of tight to fit all of them in the booth at the same time!

Deliberate "mistake": The word "Phone" is reflected the right way round in Rufus's glasses, however the word should be reversed.

Other: 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.

Continuity: When Napoleon first comes back from France and he's hanging in the tree, he disappears when the camera angle changes to an aerial view of Bill and Ted.

Continuity: In the beginning, when Bill and Ted are at the Circle K and the phone booth lands with their future selves in it, you hear Bill say "Aw, I hate that part" just as they land in the booth. At the end when we see them land to talk to their past selves, Bill doesn't say that.