Girlfriends to The Flying Nun

Dorian from Moesha appeared on episode of Girlfriends with Girlfriends' character Maya who later returned the favor and appeared in a episode 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 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.

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.

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

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

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

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

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.