My son is very good at justifying his opinions.  Just the other day, I walked into the living room to see my boy doing a headstand.....while, um, hanging out in the breeze.
Yup, that's right.  He decided that the best way to do a handstand was sans underwear.  Here is the discussion that followed.
Scene:  Upside down boy with big grin and no sense of modesty whatsoever (probably my fault) 
"Hi Mommy!  Look at me!  I'm upside-down!"
With eye rolls and a sigh, "Boy, you need to go put some underwear on."
Responding with a bigger roll of the eyes....."MOOOOMMMM.  You don't NEED underwear to be an upside-down."
He had a point there.  Technically, they are not necessary.  However, moms reign supreme. "GO PUT ON YOUR  UNDERWEAR!"