Evan doesn't wear dirty underwear

So...I have two boys that have decided that they don't wear underwear. I mean, I don't blame them. If I had my choice, I wouldn't either. I love the Bill Cosby routine about his mother always reminding him to have on clean underwear. In case he gets in a car accident or bike accident...any kind of an accident....the officer will report that the boy had on clean underwear....you don't want to have on soiled underwear! Of course, Bill Cosby says, I thought that's what an accident was!
Well I keep thinking about that moment the boys hit the sixth grade locker room and have to change out for PE. I know from experience that it comes sooner than we think. By then it will be too late to convert to tighty whities or boxers or even those new "in between boxers and briefs" underwear.
So I have started a dialouge with Evan and Cameron about which kind of underwear they want to try out. I showed them some at Old Navy and Walmart this week. Tonight as I watched them scarf down their brownies after dinner, I asked Evan, "Now, which kind of underwear do you want to wear," so I could go buy it at the store this week. He looked at me and loudly retorted, "CLEAN!" He he. At least I don't have to keep going over THAT lesson!