Inside jokes work differently than most forms of humor. It doesn’t matter if other people don’t find them funny; that’s not the point. In fact, they retain power precisely because other people don’t get them.

Done right, they can recall years of shared experiences, and therefore are rich in emotional currency. You and another, or others, become—even if only briefly— members of an exclusive club. To better understand the inside joke’s functioning, consider what happens when they fail: On The Office, hapless boss Michael Scott’s desperate winks and attempts at shared references are almost universally met with silent, stony faces. “I love inside jokes. I’d love to be a part of one someday,” he says, grinning maniacally. The problem for Scott is that his club is one t...