A joke from Son 1

The last time he was home, Son 1 told me a joke he said he had heard recently. Right away he disclaimed any responsibility for it -- "I heard this from some guy in my dorm" -- which probably makes sense, all things considered. The entire joke consists of a simple observation:

When a girl says she went through a whole box of tissues watching a movie -- and when a guy says the same thing -- they are talking about very different kinds of movies.

Yes indeed, Son 1 is fourteen years old and in high school. Where else? And yet, I haven't quite been able to get past wondering at the incongruity here: Is my kid really telling me this joke? Really? Something a little odd there, even if I can't quite put my finger on it ....