(1) how do you keep an elephant from charging?
Take away his credit card. Punagreed; the reason I picked this particular elephant joke is that it is probably the only one that is that sophisticated.
(2) what's big and purple and swims in the ocean?
Moby Grape -- Implying that the perpetrator of the "joke" is dumb enough to believe it or thinks the listener is dumb enough to believe it. this is a very cynical view of this type of joke. it's really just aimed at the childish sense of silliness, and can be appreciated by most at that level.
(3) what's the difference between a duck?
Well, for starters, there's nothing really funny there, but there's the implication that the teller thinks the listener is dumb enough to give serious consideration to an incompl.perhaps... or it just could be that it's deeply philosophical.
