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!
At one point, when they time-travel away from "1,000,000 B.C.", 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.