Mustard Check

When you have to return to the bathroom later (around 20 minutes later) to wipe your ass again to make sure you got it all. Also, when you go to the bathroom to wipe after a fart with some follow through (i.e. shart).

-Dude, my asshole is still itching after taking that shit.
-Hey man, you better go for a mustard check to make sure you got it all.