ok. Here's a joke I heard today from the teacher of the grade 7 class I work with.

2 cows are standing in a field, chewing their cud. One cow looks at the other cow and he says,"you know, all this mad cow talk is making me nervous. I'm really worried I might get it! You seem really calm though, aren't you worried?"
The 2nd cow looks back at him and says, "what do I have to worry about? I'm a penguin!"