The exploding pumpkin
It's not a euphemism for some kind of sexual act (it might be...I'll have to refer to urbandictionary when I get more time). This goes down in some classroom with a science teacher way cooler than any I had in school.
I bet he makes the students call him by his first name and stuff. Yep. Happy Halloween.
Oh...and I think it goes without saying: Don't Try This. Thanks.