Brett Baer

"New Girl" executive producers Brett Baer and Dave Finkel.

On Tuesday, Oct. 11, the worlds of FOX’s “Brooklyn Nine-Nine” (8 p.m. ET/PT) and “New Girl” (8:30 p.m. ET/PT) will collide in a special back-to-back crossover-episode event. Viewers will get to see the endearing characters from both of these sitcoms share the same screen for an hour of programming, but what they won’t see is all the hard work that went into making the crossover happen.