If you follow the Wild Mass Guessing theory that the end credits show how Panty and Stocking's mortal selves died, they could be one, despite the happy smiles of the bobble-headed chibi characters. The ending credits show them being attacked by a monster, strapped under a descending circular saw, and attacked by vultures in the desert, before ascending to Heaven, all to the tune of Mitsunori Ikeda's "Fallen Angel", a tear-jerking song in itself.
Remember kids: "EVERY SPERM IS SCARED, EVERY SPERM IS GOOD! IF A SPERM IS WASTED, GOD GETS QUITE IRATE!"
In the "Bitch Girls 2: Bitch", Corset kills Garterbelt, leaving nothing but his afro after he explodes, leading Brief to bawl and then rip on Panty and Stocking's Lack of Empathy when they show up and don't even shed a tear.