When Urkel is coming in the door with a stack of books, a woman crew member can be seen in the kitchen.
The opening scene (in the kitchen) is with Laura and Steve. To the left of Laura is a female crew member. This woman is so clearly "in the shot," she could have been mistaken for another actor.
Laura would've explained to Mr. Fleming to why Steve is acting like Elvis better if she showed him the Transformation Chamber Steve used to change into Elvis' personality.