Q. What do you get when you cross a centipede and a parrot?
A. A walkie-talkie.
Q. What do you get when you cross a pig and a centipede?
A. Bacon and legs.
Please top these. I need some new jokes.
A classic:
Q. What do you get when you cross an elephant and a rhinoceros?
A. Elephino
What do you get when you cross an insomniac, an agnostic, and a dyslexic?
Someone who stays up all night wondering if there is a Dog.
[math geek]
What do you get when you cross an elephant with a banana?
|elephant||banana| sin q
So what do you get if you cross X with Y?
Generally, a boy.
round of applause
One I saw here on the Dope:
What to you get when you cross a prostitute with a Mensa member?
A fuckin’ know-it-all.
An owl with a goat?
- A hootenanny.
A dog and a hen?
- Pooched eggs.
What do you get if you cross an elephant and a kangaroo?
Big holes all over Australia!
What do you get if you cross an elephant and a bottle of whiskey ?
Trunk and disorderly.
I don’t know if you need clean ones, but in case raunchy will do:
What do you get if you cross a penis with a potato?
A dick-tater.
What do you get if you cross a pickle with a female deer?
A dill-doe.
Did you hear about the guy who crossed an abalone with a crocodile? He wanted to get an abadile, but all he ever got was a croc-a-baloney.
A sheep and a kangaroo?
- a wooly jumper!
The Atlantic Ocean with the Titanic?
…About half way.
Bravo.
…a donkey with an onion?
Most of the time, you get a long-eared onion…
but once in a while…
…
.
you get a piece of ass that makes your eyes water 
When I first glanced at this thread title, I thought it said, “What do you get when you cross ***gen ***X with ***gen ***Y?”
Needless to say, I was very intrigued. I then realized I would have to come up with the answer to that question and I think it would have to be:
MyFaceTweets@bubbleburstdotcom
(yeah, I apologize if that’s no good…)
Old but still trusty:
What do you get when you cross an octopus with a chicken?
Enough drumsticks for everyone!
Q: What do you get when you cross a chicken with a turkey?
A: (Chicken)(Turkey) Sine Theta
(yeah, I know that one’s pretty esoteric… only someone who’s had college-level math or physics might get it…)
I don’t know, but if you’d rather do that than read the Odes and Epodes, you’re putting Descartes before the Horace.
Punchline stolen from James Thurber.