This is the second time Seymour Skinner is revealed to have previously been "cool" (as a swim instructor and principal). The first time was in The Principal and the Pauper (as a young adult). This is also the second time Bart humiliated him with a helium-filled balloon. The first was in Bart's Comet.
Although Shary Bobbins was killed, she appears in the opening sequence.
This is the second time a character was tricked into being attacked by a snake. The first was in Fear of Flying.
It is revealed that Skinner became harsh after falling victim to a prank at Springfield Elementary. This also happened to his mother in The Crepes of Wrath.
Maggie Simpson and Gerald Samson are getting along together.
Some kids from Ms. McConnell's class are seen in the flashback at the school's pool.