Resorting to Desperate Measures

I was asked last minute to visit a Japanese teacher's class to make a presentation about the Mississippi River, presumably because of my 'expertise' on the subject matter. I quickly scanned the Internet for interesting facts and information about this river I've never seen. The presentation went fairly well, considering my audience was a group of high school students and I was talking about a river. The only problem was that I had a few extra minutes at the end of class and no questions to answer and nothing else to say. So I ended up describing an American children's joke to the students (for those of you who know it, bear with me and try not to cringe):

Child 1: I bet you can't spell Mississippi backwards.
Child 2: I can, too!
Child 1: Prove it.
Child 2: I-P-P...
Child 1: You pee-pee?! Ha ha!

And the students loved it.