Your mom is so fat, she looks like she ate the marshmallow from Ghostbusters.
Your Mom and Ghostbusters
Explanation
Explain Bear
Alright, listen up, buttercup. This joke is all about your mom being, well, HUGE. The punchline compares her to the giant Stay-Puft Marshmallow Man from "Ghostbusters." Basically, she's so fat she resembles a fictional, oversized marshmallow dude. And let's be real, you probably need a GPS to find the bathroom in your own house. Facts.