A Lake Erie Monster is the biggest baddest shit that someone leaves in a toilet bowl for the next person to admire. So named after Lake Erie, one the Great Lakes because that's where the Monster swims to eventually.

Usually in context of a sexual joke, but can be done with simple procedures. Like so - stuff a woman's vagina with Mentos, then using a funnel to pour Coka-Cola, Pepsi, or any other carbonated beverage that will fizz and/or explode within her, watch the show and eat a nice movie snack such as popcorn.