Here's one I saw on Seattle's TRB:

A guy walks into a bar with his pet monkey. He orders a drink and while he's drinking, the monkey's jumping all over the place.

The monkey grabs some olives off the bar and eats them, then grabs some sliced limes and eats them. Next, he jumps onto the pool table, grabs the cue ball, sticks it in his mouth, and to everyone's amazement, somehow swallows it whole.

The bartender screams at the guy, "Did you see what your monkey just did?"

The guy says "No, what?"

"He just ate the cue ball off my pool table- whole!"

"Yeah, that doesn't surprise me," replied the guy, "He eats everything in sight, the little bastard. Sorry. I'll pay for the cue ball and stuff."

He finishes his drink, pays his bill, pays for the stuff the monkey ate, takes the monkey, and leaves.

Two weeks later he returns to the bar, and has the monkey with him again.

He orders a drink and the monkey starts running around the bar once more.

While the man is finishing his drink, the monkey finds a maraschino cherry on the bar.

He grabs it, sticks it up his ass, pulls it out, and eats it.

Then the monkey finds a peanut, sticks it up his ass, pulls it out, and eats it. The bartender is disgusted.

"Did you see what your monkey did now?" He asks.

"No, what?" replies the guy.

"Well, he stuck a maraschino cherry up his ass, pulled it out, and ate it!  Then, he did the same thing with a peanut!" said the bartender.

"Yeah, that doesn't surprise me," replied the guy.

"He still eats everything in sight, but ever since he had to shit out that cue ball, he measures everything first."