The Rich Texan's line about Hitler's car being the first car with "Fahrvergnügen" was originally supposed to be "...and it was the first car to be featured in Disney's Electric Light Parade." According to commentary, the show's legal team begged them not to use that line, despite allowing every other joke that made fun of Disney in the past. The original line appeared in the closed captions on TV (save for the syndicated version, the international versions, and the DVD version).
The car purported to have belonged to Hitler looks like an actual Mercedes-Benz owned by Hitler, seen here.
One of the carnival prizes is a mirror, which has the logo for British metal band Def Leppard.
The sign for "The Tooth Chipper" may be a reference to the Monty Python sketch "Conrad Poohs and his Dancing Teeth".
Spud says that Lisa's eyes are blue, but Milhouse said they are gray, indicating that either Milhouse is colorblind.
The nail freak who got his foot run over (and reacts to that pain instead of the pain of hammering a nail into his nostril) is the same one from season seven's Homerpalooza.
This is the second time Homer is forced to live outside in Bart's treehouse for something stupid he did. The first time was in the season five finale "Secrets to a Successful Marriage."
Homer's quadruple bypass is not only a reference to season four's "Homer's Triple Bypass," but to season eight's "The Old Man and the Lisa" where the episode ended with Homer having a major heart attack after Lisa tells him that 10% of $120 million isn't $12,000.
The "Tooth Chipper" car Bart, Lisa, and Homer were in had its bars lock low over their legs, so when they stopped suddenly, it shouldn't have hit their mouths. And how could a bar hit the teeth of two people of different heights sitting in the same seat?
Homer wouldn't be able to give Cooder and Spud the deed to the house, as he's still paying the mortgage. However, given that Cooder was squatting and failed to get a good assessment on the Simpson residence, he would have been fooled by Homer's bluff.
Only contrabass and baritone saxophones have spit valves in them (along with other musical instruments, like trumpets, tubas, and French horns). The saxophone Lisa plays looks like an alto, which doesn't have a spit valve.
The carnival in Springfield was shown to open in the morning, however carnivals don't open until evening.
When Bart crashes Hitler's car, There's a fence between the tree and the wrecked vehicle. in the next scene, the fence is gone.