This one you have to try out loud to make it funny.
It's kinda like a clean version of The Aristocrats.
"Two whales are sitting next to each other in a bar. The first whale leans over to other one and says..."
(Here's your chance to improvise: make whale sounds...ooooooiiiihhhh oooooohhhhhh clickclick click, waaaaaaaaaaahhhhhhhhoooooo ohhhhhhhhhhh unnnnnnnnnnnn nnnnnnnnnoooooohhh oh, click click click....
Go on for about four long deeps breaths, even taking an obvious deep breath between 'choruses.'
After a while, you may even need to use hand gestures to get people to stay with ya.
Finally, after an exhaustive demonstration of your whale sound abilities, end the noise.
The big finish: "The second whale looks back at the first one and says, "What did you say?"
Seriously, ya gotta try it on someone before you realize how funny it is. The best part is that it will be funniest to you!