Principal Skinner says he is glad he works in a elementary school after the 'Going postal' reference this episode aired Jan 31, 1999 long before the Sandy Hook Elementary School shooting in Newtown, Connecticut on Dec 14, 2012 but less than 3 months before the shooting at Columbine High School in Littleton, Colorado on April 20, 1999
The chalkboard gag "I will not do the 'Dirty Bird'" is a reference to the touchdown dance done by then-Atlanta Falcons running back Jamal Anderson during the Falcons' 1998 season (which led them to a Super Bowl appearance).
Homer mentions the Denver Broncos which he owns according to You Only Move Twice because Hank Scorpio gives him the team as a farewell gift after Homer told him his lifelong dream was to own the Dallas Cowboys.
Caricature artist Troy Aikman's line, "You like dune buggies? Everybody likes dune buggies!" is a reference to a similar line from a different artist drawing almost identical pictures in Season 4's "Lisa the Beauty Queen", "You like roller skating? Everybody likes roller skating!"
The Super Bowl commercial featuring three sexy women servicing a man's car had the line "The Catholic Church: We've Made a Few Changes" edited to "The Church: We've Made a Few Changes" in all reruns (and some overseas airings) due to complaints from The Catholic League, though the syndicated version has the original line (spoken and in closed captions). The uncut line is shown on the season 10 DVD set, but the subtitles/closed captions have the edited line instead.
Nelson asked the postal worker if he had ever gone on a killing spree this is a reference to going postal This originated in the USA in 1990s following a several incidents from 1986 onward, in which individuals working for the United States Postal Service workers shot and killed fellow workers and members of the public.
The use of Vincent Price in the phone message is a reference to a fake radio commercial for Coca-Cola that used sound bites of Vincent Price from his films.
In the Post Office, Krusty looks at a legends of Comedy poster an asks, "What has Fatty Arbuckle done that I haven't done?".
The terrified yell Wally, Homer, and Chief Wiggum did as they fled from Rupert Murdoch's private room is a reference to the terrified yell Larry, Moe, and Curly Joe did, from The 3 Stooges.
Al Gore measuring the Drapes of the Oval Office is a reference to the fact he was running for President at the time (he lost the Presidency to George W Bush by 500 votes in Florida although he won the popular vote nationally).
The appearance of a character named Rudy who wants to get on the bus with the others with the line "What I lack in size I make up for in obnoxiousness." is apparently a reference to, and commentary on the main character of, the film Rudy, with Sean Astin.
When Bart's class is on the field trip at the post office, at one point, Chuck is among the students seen there, but he isn't usually seen as part of Bart's class. It was a full-school field trip. This is evident, as Lisa was shown there.
Ned Flanders is seen to have a lot of hidden body fat in this episode, but most episodes to have him shirtless depict him as very muscular.
When everyone is drunk on the bus, the Blue-Haired Lawyer's glasses have black rims in this episode instead of the usual green ones.
When Marge suggests the Color-By-Numbers kit to Lisa, she is instead holding the Li'l Leonardo Art Set. After the camera changes, she is actually holding the correct Color-By-Numbers kit, but another Color-By-Numbers kit is also seen behind her.
When Marge and Lisa look through art kits, in one shot when Marge is behind the Leather Craft set her arm is drawn in front of it, revealing it not all the way drawn.
Why didn't the fans kick Wally Kogan while being housed in the jail? He was the one responsible for getting the tickets, not Homer. It somehow has to do with the fact that Homer signed them up for the trip.