Steve says he's had perfect attendance in high school, but in the season 5 episode, "Hell Toupee", he and Myra ditched. In the season 6 episode, "My Bodyguard", he was absent several days.
3J's name is revealed to be Jared Jamal Jameson, which is not mentioned again in the rest of the series.
In this episode (and the next episode, "Eau De Love") it's mentioned that Carl and Harriette have been married for 25 years, but just last season, in the episode "Ain't Nothin' But An Urkel," they'd been married for 22 years.
Steve and Carl are in the Winslow's living room when Steve accidentally takes Laura's diet pills. After he takes the pills Steve clips his water bottle on the left side of his tool belt and clips the pill bottle to the right side of the belt. Steve then exits the living room to meet Carl in the garage. When Steve enters the garage the two bottles are suddenly reversed! The water bottle is now clipped on the right and the pills are on the left.
In this episode Steve says he doesn't know how to ride a bike, but in "Finding the Words" he says he rode his bike down Elm Street.
When Steve is walking on the roof in the opening shot, you can tell that the snow is just sheets of cotton when he walks over it. The 'real' snow is obviously fake here, unless it's part of Steve's display.
In this episode Maxine says to Waldo that she's going to graduate in secondary, but two episodes after, "Friendship Cycles", she says that she's going to a beauty school.
In the scene when Carl and Harriette are talking in the kitchen, she is wearing big, gold dangly earrings. If you listen carefully, you can hear the left one fall off and hit the floor, but when Harriette goes to sit at the table, the earring is back on.
When Carl is being audited by the IRS he says that Richie's mother, Rachel, lives with them. However, Rachel—all through seasons 5, 7, and 8—is nowhere to be found and not even mentioned like she did not even exist.
In the first classroom scene, the room number on the door is 214, but in the second classroom scene when Steve is teaching, the room number has been changed to 213.
When Stefan walks in the classroom, the only thing on the chalkboard is the drawing of Steve Urkel with the phrase "Jerkel" pointing to him. But when Stefan begins to teach, his name suddenly appears on the chalkboard, but we never actually see him write his name on there.
Although it was a fantasy in Steve's mind, he talks in his real life voice, saying "Thank you"
What happened to the shower Carl built Mother Winslow in the first season? That would suggest that there were at least two bathrooms in this house. Regardless, wouldn't Steve or Laura had secured the lock before dropping the towel?
One scene showed a potato chip can and the next scene it showed the can tipped over and then again back to its original position.