Two little boys, ages 9 & 4, go to the supermarket.  The 9yr old grabs a box of Tampons from the shelf & carries it to the checkout counter.

The cashier, thinking this is a bit unsual an item for such a young boy to buy asks if they are for his mom.  

"Nope." the boy replies.  

"Oh well, then they must by for your sister?"

"Nope, not for her either." replies the boy.

The cashier, by now really curious says "If they're not for your mom or your sister, who are they for?"

"They're for my 4yr old brother."

"I can't imagine they'd be for your brother.  Do you know what these are for?"

"Sure." the kid replies.  "I saw the ads on TV & they say that if you wear these you will be able to swim & ride a bike.  And my little brother can't do either."