The song everybody else sang, when Sherri and Terri got sprayed by a skunk in a cookie box, is a parody of Jingle Bells.
The watermark that says "Only You can Prevent test fraud" references Smokey the Bears famous quote: “Only you can prevent wild fires.”
When Homer draws a picture of himself it looks similar to his original look. Originally, Homer was going to have a G for his ear and the M on his hair and it would form Matt Groening's initials. However, as explained in the audio commentary for "Lost Our Lisa", the design was dumped as it would be to distracting for fans.
Bart has no friends
The last time Lisa imagined herself fat and being with a boy who has a crush on her and denied the fantasy happening was in "Lisa the Simpson". This is also the last episode where Lisa was concerned about her Simpson DNA.
Second episode where Marge brings a kid she bonded with to the Simpson house, much to Bart's dissatisfaction. First was "This Little Wiggy" which in that episode it was Ralph Wiggum. In this episode, it is Nelson Muntz.
Eddie Muntz’s allergy is revealed to be peanuts.
Nelson mentions his deceased sister.
When Sherri and Terri are running away from the skunk, Terri has a purple hand.
Homer drew a simple black and white sketch of himself, but when he talks to Lisa, his drawing is colored.
Homer was seen eating a sandwich, but the sandwich had toothpicks, therefore, Homer would’ve ended up in the hospital.