You should pack a 'change of underwear'. [=additional underwear that you can wear at another time]
He answered the door 'in his underwear'. [=while wearing only underwear]
(..) If he won't tell ya something, cut off one of his fingers. The little one. Then tell him his thumb's next. After that he'll tell you if he wears ladies underwear. I'm hungry. Let's get a taco. Fuck. Jesus. I'm blind, man. (..)1992 Reservoir Dogs