Because they're funny on many levels.
I still find you dashing
Give her a couple of test tickles...
One, but you can be sure a whole Reddit community will appear to expand the joke, make it funnier and eventually run it into the ground.
THEY BOTH LICK THEIR PAWS!
He couldn't fit in the elevator.
I think I'm coming down with something.
They work on so many levels.
Because they work on so many levels