(but it made me laugh)
Q: What is E.T. short for?
A: Because he has little legs!!!
Actually, there was a 12-year-old boy without legs inside the costume for some of the scenes.
So that's another reason.
But I'm not sure if that information makes the joke funnier or not.
If this is not hilarious enough for you and you want something else that (1) isn't funny and (2) has to do with E.T., perhaps this is the place for you?