One who is about to take a dump.
"Johnny is such a brownie baker, you are sitting by him on the way home."
an alternate way to say fudge packer. because the meaning isn't as well known, you can actually call someone a brownie baker to their face and they will be oblivious.
Kevin, the brownie baker, wears those sparkly shirts and masturbates to gay porn in his dorm room all the time; what a tool.