There was a cut gag with the Homeless guy looking at a store's window, where he rambled on about peanut butter.
The "Fish that swim up your wiener" are actually real. They are called "Candiru Fish". They are common in South America and do the same as what Bart mentioned. But rolling around in the snow naked is not the cure.
Bart gets a haircut from the old ceiling fan. The last time he had a haircut was in "Blazed and Confused".
After getting a haircut, Bart wears his red hat right up to the end of the episode. The last time he wore it was also in "Blazed and Confused".
At the car crash scene, when Marge was talking with Chief Wiggum, The crash was a head-on or a rear-end impact between a red and a purple vehicle, but when Marge start cleaning the scene, It's a T-bone crash.
When Marge was talking with Clancy, there were two ambulances and one fire truck at the crash site, but when Marge starts cleaning the scene, there's only one ambulance.
The buildings surrounding the crash change appearances between scenes.