Hey, It's That Guy!: One episode features Urkel facing off against a group of bullies lead by Jason David Frank, whom most children of the 90s know as Tommy Oliver, the breakout star of the Power Rangers franchise.
I Am Not Urkel: This series pretty much killed any shot at Jaleel White being taken seriously as an actor, outside voicework.
Although slightly subverted as White doesn't resent his most famous role and has fond memories of the series.
The Other Darrin: Jo Marie Payton, the original star of the show, left halfway through the show's final season and the role of Harriet was recast with Judyann Elder. Much less dramatically, the actor playing Richie was originally a pair of twins, since he was a baby during the first season. The character went through Soap Opera Rapid Aging Syndrome after this and he was recast with four year old Bryton McClure.
Recycled Script: As with all Miller-Boyett sitcoms, the producers weren't shy about recycling ideas from other sitcoms. The season 2 opener, where Urkel burns down the Local Hangout and it's rebuilt as the cooler "Rachel's Place," was virtually identical to a story involving Arnold's on Happy Days, which several of the writers had worked on.