Hey, and while we're on the base, I'll visit my grandfather, Enos. He was stationed at Roswell.
Your grandfather? [He leaps up.] Stay away from him, you dim-witted monkey. You mustn't interfere with the past. Don't do anything that affects anything, unless it turns out you were supposed to do it. In which case, for the love of God, don't not do it!
Got it.
If, for example, you were to kill your grandfather, you would cease to exist.
[Fry gasps.] But existing is basically all I do!