Funniest one I've heard for a while...

A vampire bat comes back to the cave, covered with blood from head to foot. All his mates jump up, shouting, "Wow, well impressive! So much blood! Where did you get that?"

"Shut up, I'm knackered, I just want to sleep."

"Come on, tell us."

"No, get lost."

"Go on!"

Eventually the bat gives in and says, "OK, follow me." All the bats eagerly follow him as he flies through the forest. He stops in the darkest part of the forest, in front of a tall tree with almost-black bark.

"OK, do you see this tree?

"Yes, yes!" shout the other bats eagerly.

"Good. Because I bloody didn't!"