Someone who is impossable to communicate with when they are under the influence (Taken from the chimpanzees used in the early days of teh space program who were impossable to communicate with when they were in orbit).
Jerry's gone space monkey on us. Three tequilas and he's in his own orbit!
a monkey from outer space. they smell of asparagus, wear large earmuffs, are fluent in spanish and can sing and dance "god save the queen" on top of a soup can without falling over more than four times.
Someone so into New Age ideas, psychedelics, or other alternative thought system that he or she becomes out of touch with reality. Also called Space Case.
Roommate: Are you even paying attention to me? You need to pay your share of the electric bill, NOW.
Space Monkey: Have you ever asked yourself, does the electric bill even exist, or is it all in our minds? What is a bill made of? If the bill could sing, what would be its song?
Roommate: Dude, that's it, I'm kicking you out, you flippin' space monkey.