Transcript:
Boy: Dad, why is it "pants" and not pant? I mean, they're like one thing, right? Man: Because if you change "pants" to "pant", pretty soon "deer" becomes "deers", and all of a sudden we don't speak the same language, and our civilization crumbles.
In the U.K., “pants” refers to underpants and the outerwear is called “trousers”. So if someone from England starts giggling when you talk about your pants, that’s why.