Hangin' with Mr Cooper to Step by Step

Michelle Tanner from Full House appeared on an episode of Hangin' With Mr. Cooper in which Mr. Cooper was her substitute teacher.

Steve Urkel visited Stephanie Tanner of Full House to convince her that glasses could be cool

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.