Context:

When someone refers to an ambiguous, undefined “we” in conversation, one would pose the question: “who’s ‘we,’ you got a frog in your pocket?”

Origin:

The informant learned this humorous saying from her dad, who himself learned it from his law school roommate. Though he attended law school in Dallas, Texas, the person who introduced it to him hailed from Southern California.

Interpretation:

Though this saying seems nonsensical, it allows asker to pose the question “who is ‘we’?” without the natural implication of suspicion or aggression that might be invoked by the question by itself. Similarly undercutting tension, it reminds the person being asked that they have neglected to provide relevant details in a manner that is humorous and non-accusatory.