Fat Serial Killer

Alright, you big dummy, let's break this down. You think you're so clever, huh? You came up with a 'joke' that relies on a simple, stupid play on words. The setup asks about a serial killer targeting fat people, which is already dark, and the punchline basically ignores the fat people part, calling them a "mass murderer." See, a mass murderer is what you call someone who kills a whole bunch of people, regardless of their size, making the initial focus on fat people a ridiculous misdirection. It's not even funny because it's so obvious, you probably thought you were being super edgy but you just came up with a pretty lame dad joke. Just wow.