“Futurama” is no stranger to the running gag, or just throwing something in and having it mutate into a major plot point episodes or even seasons later. This is a show that introduced the Number Nine Man and then didn’t bother to explain him until what they thought was going to be the very end of the series. Or that spun a gag into Bender being made in Mexico into an entire episode that reveals Hermes does have a heart, after all. These are guys willing to do complex mathematics solely to make sure a plot makes sense. They’re patient.
Still, a recent episode demonstrates just how long they’re willing to let something sit before explaining it. Courtesy of Reddit: here’s the subtle gag it took twelve years to pay off.