Leonard's hair changes back and forth between orange and blue.
When Mrs. Helperman is about to announce the winner, Scott is standing in front of the class next to Ian and Leonard. When she finally announces the winner and the entire class cheers, Scott can be seen sitting at his desk cheering along with the rest of the class. Afterwards he's back at the front of the class standing next to Leonard.
Spot gets opposable thumbs when he's Scott.
Where did Spot get his glasses?
Leonard says he's 10 years old, but he didn't turn 10 until Party Animal.
How does Fifi know Leonoard's clown act isn't funny? She's never seen it.
Normally, passwords would be hidden.
Mary Lou (Leonard's mom) wakes up without any slippers, then puts some on to call the substitute. Then, she comes back in, gets out of the slippers into the bed. Later, when Mr. Jolly grabs the blanket and rips it off, Mary Lou's slippers are on again!
Why didn't Leonard simply make the excuse to his mom that he was holding the big science fair project for Scott Leadready II? Technically, Spot was planning on presenting his science fair project as Scott, and NOT as Leonard's dog!
In Principal Strickler's office Leonard's mom has black feet!
This episode title is a reference to the play The Night Before Chrismas.
The pizza they sat on was only there when they sat on it. It was never there before.