Mork & Mindy to Shake It Up

Mork's character originated from Happy Days

Perfect Strangers' featured a game show segment in which the toilet was provided courtesy of Cunningham Hardware in Milwalkee, WI, owned by Howard Cunningham of Happy Days.

Family Matters was a spin-off of the character of Hariette and Carl Winslow from Perfect Strangers

The family from Step by Step was in the middle of a barbeque outside when Urkel from Family Matters came (literally) crashing in on the jetpack he had built on the last episode of Family Matters.

Boy Meets World and Step by Step both had episodes at Disney World and whiel in Disney World Eric from Boy Meets World met Dana from Step by Step.

Boy Meets World was continued decades later in Girl Meets World

Austin and Ally appear on an episode of Girl Meets World. Bringing the Disney Channel Live Action Universe into the Westphall Universe

Jessie and Austin & Ally crossed over

Good Luck Charlie crossed over with Jessie

Shake It Up characters appeared on Good Luck Charlie