"X-Cops" (X-Files and Cops)
In a monster of the week story, Mulder and Scully are interviewed by the reality TV show during an investigation. Mulder embraces the publicity while Scully doesn't think their work should be on national TV. Like Cops, the episode is shot on videotape and unfolds in real time.
“The Night Shift” and "Homecoming" (Brooklyn 99 and New Girl)
Jess Day and her friends head to NYC for an event at Schmidt's old high school. Hijinks ensue when Jess crosses paths with the 9-9's Jake Peralta.
"The One with Two Parts: Part 1" (Friends and Mad About You)
Mad About You's Jamie and Fran stop by Central Perk and mistake Phoebe for her twin, Ursula, the flaky waitress at Riff's.
"Something Good Coming: Parts 1 and 2" (Community and Cougar Town)
In Season 2 of Community, Abed tells Jeff that he was on an episode of Cougar Town and soiled himself. More cameo than crossover, Cougar Town incorporated Abed into a scene, and even had him running away post-accident.
"Stephanie Gets Framed" (Full House and Family Matters)
Steve Urkel not only helps Stephanie deal with new glasses, he also dances it up with Uncle Jesse. Have mercy!