If he's very young he probably just saw you put one into your panties and wanted to imitate you. Just calmly explain to him how menstruation works (and no, it's not "eww" or shameful). If he's like 15 and you've never talked to him about it before: YDI (no, it's not the school's job nor will he magically know). If he's like 15 and knows what pads are for: Yeah, no idea man. Maybe a dare?

If he's very young, like preschool or kindergarten, I've heard of kids afraid of wetting their pants using them. If he's a teenager, there's some thing where guys have decided to wear pads during their girlfriend's periods to "show support." It's a little strange, but would show he's trying to be sensitive.

Good for absorbing butt sweat!!!

One way to eliminate skid marks.

Today, my mom looked inside my underwear. FML

He could have the *****- and was prepping for future explosions

this is understandable but odd. A common issue guys have is the whole shake after. no matter how well or many times u shake you WILL have drops in ur underwear; even if a little. i wore white underwear as a kid and we all have yellow pee at some point. kinda smart really to avoid problem :). im not sure if being circumcised effects...

He either needs a lesson in anatomy. Or He made a makeshift codpiece. In that case it's a talk about confidence. But you have to talk to him in private. Like others said this all age dependent.

he's preparing to eat a bunch of potato chips made with olean or olestra!. . .or the haribo sugar free gummy bears!

He needs chipotle away...