The monkey and the pool ball
A man walks into a pool hall with a monkey on his shoulder. He approaches a table to play a game, and sits the monkey down on the table. The monkey reaches into one of the pockets pulls out a ball, sniffs it, and then swallows it. The man calmly pays the owner for the lost ball and leaves.
The same man returns a week later with the same monkey. This time he sits at the bar for a drink, and the monkey takes a peanut from a tray then inserts it into his ass, then removes it and eats it. The bartender notices this and asks the man about the odd behavior.
The man replies “Ever since he swallowed that pool ball, he measures everything before he eats it”.