Caprica to KC Undercover

Caprica was a prequel to Battlestar Galactica

Battlestar Galactica's pilot had a scene showing a Firefly class ship flying over

Weyland-Utani is a client of Angel's Wolfram & Hart and also the company that made some of the weapons used by Firefly's Malcolm Reynolds in the Battle of Serenity

John Larroquette Show referenced Yoyodyne. Yoyodyne was also a client of Angel's Wolfram & Hart.

John Larroquette Show's John Hemingway called into Fraiser's show

Cheers spun-off Frasier

St Elsewhere's Westphall, Craig and Auschlander visited Cheers' bar

The Bob Newhart Show's Elliot Carlin visited the psych ward at St Elsewhere's St Eligius Hospital.

The Bob Newhart Show's Bob Hartley woke up after dreaming the entire series Newhart during Newhart's finale.

Newhart's Larry, Darryl and Darryl squatted in Coach's Hayden and Christine's home

On a network crossover night, The Drew Carey Show, Grace Under Fire's Grace Kelly, Coach's Luther and Ellen's Paige and Spence all show up. Finally on Ellen, Paige and Spence run into Grace Kelly and Drew Carey

The Drew Carey Show's Mimi appeared in an episode of The Hughleys

The Hughleys crossed over with The Parkers.

The Parkers was a spinoff of Moesha

Hakeem and Niecy from Moesha went to the prom with Cher and Sean from Clueless.

Sabrina from Sabrina the Teenage Witch visited Cher from Clueless in the episode "Mr. Wright."

Sabrina the Teenage Witch also crossed over with Boy Meets World on several other occasions.

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

Ernie and Judy from KC Undercover appear in the Halloween episode of Austin & Ally, "Scary Spirits & Spooky Stories"