My idea stemmed from a comic a buddy and I were developing called TimeGeeks... which may or may not someday see the light of day.
Basically, he and I got into a conversation about what we'd do if we had a time machine. I would go back and get old issues of X-Men from the 60's and he'd go and watch Star Wars on opening night in the seventies. We wouldn't visit historical events or solve ancient mysteries. We'd simply be geeks in time.
We had a bunch of ideas based on it, but one of my favorites was that his character would travel back in time to warn George Lucas of the dangers of including Jar Jar in the prequels. Unfortunately, Lucas would be so intrigued by the concept of Jar Jar, that we would fundamentally alter Empire Strikes Back to include him in it.
Now, the TimeGeeks wouldn't know this until traveling back to the present and watching Empire. Couple panels of us staring horrified at the monitor and then my character shouts "CHANGE IT BACK! CHANGE IT BACK!"
We'd mess with Lucas a whole lot and everytime it would have hilarious results. On possible future included Star Wars Episode 7 where Lucas intentionally makes a crappy movie so that the fans finally leave him the hell alone. It features a cast made up almost entirely of Jedi Ewoks and the plot doesn't even try to make sense.