Your body's natural defense against stupid.
You walk into a hospital room where your friend is on a bed with his left leg, no arms, and only half of his prick. You say,"How ya doin, man?"
He says,"Oh, just great. I feel better than ever. I could just hop all around the world, I feel so great."
You say,"Really? That's some great news."
See, this isn't your friend trying to make you look stupid, which if you said one or both of these things, you might be, it was his immune system acting due to the high levels of stupidity being taken into his brain. It automatically responded with sarcasm. So don't take it personaly.
What happened that time in seventh grade when you walked in on your parents.
"Hey, guys. I need... What are you two doing? OH MY GOD ARE YOU...AHHHHHHH!!!!!!(puke)