A man walks into a bar with a monkey on his shoulder. The bartender says "hey you cant bring pets in here!" The man replies "dont worry, hes trained. He wont mess anything up." The bartender agrees to let the man and his monkey in. While the man sits down, the monkey hops on the bar and eats a cherry, then jumps on the pool table and swallows the cue ball whole. Furious, the bartender says "get your monkey out of here! I cant have him eating things like that."

A few days later, the man enters the bar again with the monkey on his shoulder. "Didn't i tell you to get that monkey out of here?" The bartender asks. "Its okay," the man says. He wont do it again. The monkey hops on the bar, grabs a banana, shoves it up his, pulls it out, then eats it. "What the hell is he doing?" asks the bartender.
"Measuring." the man replies. "You would measure too if you had to pass a cue ball."