This is like a forum game I a while back: Somebody makes up a strange question, and the next person answers it with a strange response, like this:
1P: What do you call it when Star Wars meets Star Trek?
2P: Watch Independece Day, and then you'll get an idea.
2P: What do you call it when a large rat has static electricity in it's fur?
3P: Say hello to the first Pokemon!!!
We'll start with this one:
What do you call it when a rat get's into a cactus garden?