Taco Bell Donut
The ring of fecal matter that permanently attaches to your toilet because your roommate didn't flush after shitting out his 1am grande meal, in fear of waking you up. The Taco Bell Donut also has a unique stench.
Bob: "I see you have a rust ring in your toilet, did you try CLR?"
Stan: "That's not rust. It's Ed's Taco Bell Donut he left last week. I'm not touching that."
Stan: "That's not rust. It's Ed's Taco Bell Donut he left last week. I'm not touching that."