When Lou is being sent off, Bart says, "Here's lookin' at you cud," which is a reference to Humphrey Bogart's famous line, "Here's lookin' at you kid."
The blackboard gag is a reference to 'Horton Hears a Who' by Dr. Seuss.
Mary's middle name is "Wrestlemania" which is the biggest pay-per-view of WWE.
As Lou leaves on the flight to India, the national anthem of France is played instead. This is a reference to a similar scene from the end of Casablanca and not a mistake or joke.
According to Marge, Bart "still sits in the driveway and pretends to drive the car".
Brandine Spuckler was 13 when she married Cletus and she had already been divorced four times before that, and his father. However, this is probably a criticising reference to yokels marrying over and over again.
The animal sound tape Lisa played for Bart said "Tress MacNeille" on the cover and when Homer is entering the killing floor of the slaughterhouse he hears a voice say "You are now entering the killing floor", Homer then comments "Hmm, that sounds like Tress MacNeille". Tress MacNeille is a voice actress on the show who voices lots of extra-characters as well as some recurring characters such as Dolph, Agnes Skinner and Mona Simpson.