Here's the one that so tickles my funny bone:
Little Jimmie asked, "Grandpa, can you make a noise like a frog?"
He replies, "Well, yes Jimmie, but why do you ask?"
Jimmie answers, "Well, Grandpa, I heard Mommy and Daddy talking, and they said that when you croak we're all going to take a trip to Hawaii."
It happens very rarely - I suppose because of the risks involved, but the CBC, on am690, asked callers to tell one of their favorite jokes, on air. This is the one I told, and I have great difficulty telling it because I laugh so hard that I have trouble with the punch line. The show host immediately asked me for another but, being a family program, and with my limited cache, I had to decline.