Black Olive Theory
The theory that if one partner in a relationship likes black olives, and the other doesn't, the relationship could work out. If neither party likes, or both parties hate, black olives, according to the theory, their relationship is doomed.
Bro 1: Hey bro, how do your parents get along so well?
Bro 2: Black olive theory, bro. My dad loves black olives and my mom hates 'em.
Bro 2: Black olive theory, bro. My dad loves black olives and my mom hates 'em.