unicorn sperm
The sperm of a unicorn has magical properties in which the "catcher" can start to read peoples' minds and even input thoughts into the minds of others; it can even go as far as reaching the person's dreams (inception-like symptoms)
Roommate 1: "Dude, what the hell is unicorn sperm doing in a baby food can in our refrigerator?"
Roommate 2: "No."
Roommate 2: "No."