Of all the movies and shows to explore the power of time travel, it should be embarrassing to the entertainment industry as a whole that Bill & Ted's Excellent Adventure, a movie about two time traveling morons, has done a great job of it.

During the movie's climax, Bill and Ted realize they need some help getting out of some sticky situations. Knowing that they have access to a time traveling phone booth (seriously, entertainment industry, be embarrassed), the dimwitted duo make mental notes to later use that phone booth to go back in time and leave themselves helpful objects (keys, etc.).

Brilliant!

Bill and Ted realize that their present will, in the future, become the past. And from the future, when it is the present, they can return to the past to help themselves in that past, which from their original perspective is the present. Why don't all time travelers realize this?

To further the point, during a battle with their nemesis, Bill and Ted have to outwit the villain who is also using this technique. One might think, "Well, Bill and Ted's mental notes are predicated on the assumption that they're successful. And the villain also assumes he's successful. Isn't this a flaw in the movie's time travel technique?"

One might be wrong.

Bill and Ted, knowing the villain also makes the assumption, trick the villain by providing him with a harmless version of his plan (planting a gun, I believe). Bill and Ted, I imagine, had to assume their success, then remember to later go back in time, find the villain's planted gun, then swap that gun with a gag gun. That's some impressive temporal mental acrobatics for a pair of air-guitaring fools who can barely pass high school.

Bill & Ted's Excellent Adventure is certainly not an example of time travel done right in all facets, but I think on this particular point, they have a leg up on some other movies and shows. I'm looking at you, Star Trek. Perhaps the Federation could use some of its many methods for time travel to apply Bill and Ted's principles and avoid wars, defeat the Borg, and save "Enterprise" from cancellation.

Yeah, this keeps me up at night.

PS: While writing this post, I came across an interesting article: Temporal Anomalies in Time Travel Movies unravels Bill & Ted's Excellent Adventure. It makes some good arguments, but I just spent about an hour writing this post so we'll have to agree to disagree on some points.