The Australian zookeeper is an obvious parody of Steve Irwin.
After a three-toed sloth was accidentally shot in the butt with a tranquilizer dart (intended to be for a charging rhinoceros), it briefly undergoes a jig mirroring that of Snoopy from the Peanuts franchise before falling asleep.
When all the teachers and staff members come out on stage for the musical in the beginning, there are nine people, when they form a pyramid there are ten people.
When Marge first used her headlights to see Bart and Lisa in the kitchen, Bart was wearing nothing but his underwear (and the chicken he wore as pants). But when Bart is stealing from Marge's purse, he is fully clothed.
When Eddie the cop (as Curtis E. Bear) was being bludgeoned with 2x4's at traffic school, Krusty's nose was the same color as his skin before Agnes knocked Eddie down.
In this episode, Homer is disgusted by Mrs. Krabappel's balloon striptease, but in "Bart the Lover" he was the one who drooled over her lingerie picture that she sent to "Woodrow".
When Homer is talking to Bart while Marge uses her new headlights, Bart's legs disappear when he is talking.
When Homer is driving in the Springfield Nuclear Power Plant parking lot, all the Canyonero windows are tinted, but when he starts talking to Lenny and Carl, the windows are transparent.