The Flying Nun to The Walking Dead

Both Gidget and Sister Bertrille from The Flying Nun mentioned in their respective shows that they were members of a rock band called The Gorries.

The New Gidget was a sequel series to the original Gidget after 20 years

Gidget and her family went on a cruise on The New Gidget and ended up on Gillian's Island.

Meego (who was an alien) tried to contact his mother on the home planet by phone and instead the phone connected with Gilligan, Mary Ann and the Professor on Gillian's Island

Family Matters' Urkel appeared in the first two episodes of Meego.

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.

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

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

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

The Parkers was a spinoff of Moesha

The Hughleys crossed over with The Parkers.

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

The Drew Carey Show did a cross over with Coach.

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

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

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

St Elsewhere's Dr Turner was investigated for murder by Homicide's Pembleton and Bayliss.

Homicide's John Munch questioned The X-Files' The Lone Gunmen.

Morleys