A man with a monkey walks into a bar. The monkey jumps up on the pool table and swallows the cue ball whole. The bartender looks to the man and asks "WTF was that?" To which the man replied, you never know what a monkey is going to do.
Two months later, the same man returns to the bar with his monkey. This time the monkey grabs a beer nut, studies it, shoves it up it's butt, twists it around, pulls it out and proceeds to eat it.
The bartender asks why on Earth did he do that. The man replied, "well, ever since the cue ball incident, he likes to check his food for size".