crumbs in the butter
Fast food remnants that get lodged in unwanted crevices while having anal sex in a vehicle, typically while wearing a Snuggie.
I was really going at my wife's ass in the car the other night, wearing a zebra Snuggie, until the crumbs in the butter chafed my dick.
Crumb butter
The reminance of unused butter that has been scaped off the knife and resides on the rim of the butter tub
Me: We've run out of butter
Gf: Have you used the crumb butter?
Me: No, im not homeless
Gf: Have you used the crumb butter?
Me: No, im not homeless