When you are giving you're grandmother anal, often times her prostate gives out and she will shit all over your dick, proceeding her to suckthe shit off your dick and calling them grandmas brownies.
Pizza that someone eats after it has been left out for several days (aged) and resembles 'Grandma' with it's funky odor, fuzzy surface, and rigid texture.
John: Dude, What's that smell!!
Mark: Oh, It's probably this slice of Grandmas Pizza I found.
John: And you're eating it? Good God, It's starting to grow things on it!
Mark: ..it has character.