We were playing Chrononauts on Friday. In that game, you can prevent WWII by stopping Hitler, which happens (and un-happens) just about every game. Usually, people assassinate him.
We got kind of sick of that after a few games, and started getting creative. We bought his art and put up an exhibit in the Louvre. He never got into politics and led a fine, creative lifetime in which he saved John Lennon's life.
This got me thinking, and now I realize why so many celebrities are insane and untalented:
They're being stopped from committing horrible crimes. Britanny Spears would have slept with President Bush and convinced him to invade Canada. Carrot Top would have invented insane nuclear-missile-controlling robots. Mel Gibson would have... repeated history. "President Gibson", a name that suddenly becomes a pun.
So time travellers subtly went and altered their paths. Hiring them for this and that, spending a bit of cash on them, driving them into new careers where they are no threat to anyone.
See? It's all so clear! Yeah!