Postcards From the Wedge

Postcards From the Wedge is the fourteenth episode of Season 21.

Plot
Homer and Marge receive a letter from Edna Krabappel informing them that Bart is one month behind on his homework. When Homer is informed that he does not have to help Bart with this work, he is eager to increase his son's workload. Marge, however, is concerned that the heavy workload will dissuade Bart from liking school. When Bart realizes his parents do not agree on this issue, he uses their opposing views to avoid homework entirely. Lisa explains that this is a wedge issue, that is, an issue that sharply divides two parties.

Marge and Homer begin to argue more and more, with Bart inciting the two to argue about very minor things. Marge seeks council from Ned Flanders, who recalls having a minor argument with Maude on the day she died. He mentions that this argument still haunts him and Marge decides to apologize. Meanwhile, Homer dreams about accidentally killing Marge and realizes that he too wants to apologize. The two spot each other in traffic, rush out of their vehicles and embrace. They then decide to let Bart fend for himself.

When Bart realizes that neither parent will react to his misbehavior, he and Milhouse play a prank on Principal Skinner. To evade capture by Skinner, Bart and Milhouse hide in the abandoned Springfield Subway System where they discover the subway trains still work. They race down the tracks and cause a seismic tremor to shake the town. When Homer and Marge fail to react to this, Bart confesses to Nelson that he no longer feels a thrill when he plays a prank. Nelson suggests Bart receives no gratification from pranks unless someone gets angry.

Bart decides to destroy Springfield Elementary, which was damaged by the first subway tremor, by driving the train under it. Homer and Marge find a note from Lisa informing them of this prank and they decide to stop ignoring Bart. They rush to the subway station, where Homer pulls the emergency kill switch. Bart is grounded but is happy that his parents are paying attention to him once more. At the end, Lisa reveals that Bart wrote the note about the subway prank, suggesting that he wanted to be caught but promising to keep it secret to protect his bad-boy reputation.