Peer pressure

I was surfing the web and found something I thought was funny:
Q - Why did the monkey fall out of the tree?
A - Because it was dead.
Q - Why did the second monkey fall out of the tree?
A - Because it was tied to the first monkey.
Q - Why did the third monkey fall out of the tree?
A - Peer pressure.
(I found it here)

I don't know; maybe this is less funny if you are fully awake.