It's referring back

"It's referring back" -- Jon Reddick

Origin

Sometime in the mid-1990s, USS Khai Tam Captain Jon Reddick explained to a group of shipmates that sometimes things were funny because they referred back to an earlier anecdote or joke. The explanation in and of itself was fairly innocuous, but shortly thereafter, Jon made one of his well-timed comedic quips which indeed referenced an earlier anecdote. As the laughter began to subside, Jon added, "See? It's referring back," adding a hand gesture flipping his palm from upwards to down-and-backwards. The laughter picked up once again, and the comment and gesture became a theme for the evening.

Nowadays, Jon and some of his old Khai Tam friends still use the line, but more frequently when the joke which "refers back" has fallen flat and needs some help to get a laugh.