In the punchlines.
Once in awhile.
One if nobody is watching.
Because it was crumby.
WRONG! They don't make it, they steal it...
They Planet.
Me: Partying with Friends Pimple: Ok, I'm Also Coming then!!
If she's only wearing one sock. (This joke brought to you courtesy the homeless guy outside my local 7-11.) Edit: tweaked the punchline.
I think it's because usually the punchline is too long
He had no patients
Just one. He holds up the bulb and waits for the world to revolve around him.