The Bob Next Door

""The sum total is the greatest murder since Snape killed Dumbledore!""

The Bob Next Door is the twenty-second episode of Season 21. It originally aired on May 16, 2010. The episode was written by John Frink and Nancy Kruse directed. Kelsey Grammer returns as Sideshow Bob, and David Cross voices Walt Warren.

Bart becomes convinced that his new neighbor, Walt, is his archenemy, Sideshow Bob, disguised and back for revenge. But when Marge tries to convince Bart otherwise by taking him to the state penitentiary, a disturbing truth is revealed, leading to danger for the spiky-haired boy.

Plot
Springfield is suffering from an economic crisis so massive that the Quimby Administration could no longer hide it by cooking the books and fudging the numbers. Mayor Quimby enacts cost-cutting measures such as stopping the service of removing dead animals from the road, drastically shortening the school day at Springfield Elementary School (to the extent that the only "school time" was the bus ride over to the School Building), and ordering Springfield Penitentiary to release prisoners convicted of minor offenses. The Springfield Police Department is also affected by the cutbacks, being forced to allow low-level criminals to get away with crimes, due to lacking the resources -- and especially the funding -- to go after them.

Many citizens move because of the cutbacks, and a house next to the Simpsons' goes on the market. Homer decides he wants to buy the house because of the smell of cookies coming from it, but someone's beaten him to it. The Simpsons have a new neighbor, Walt Warren, who closed the deal on the house while Homer was filling out the loan paperwork. Also, at least one of the banks in the world that received Homer's loans, the Iceland National Bank, closed down due to not having enough money, causing the populace to want to kill Homer Simpson.

Marge and Lisa watch movers (and Walt himself) carrying personal possessions into the house, and conclude that Walt is a lover of antique furniture and koi ponds. Bart, however, believes that Walt is actually Sideshow Bob as soon as he hears Walt's voice. Bart decides to unmask Walt as Sideshow Bob. He first tries singing Gilbert & Sullivan music, knowing that Bob has a fondness for it and figuring that he won't be able to resist joining in. When that doesn't work (and Walt says he likes country music instead), Bart then sneaks into Walt's house looking for proof but gets caught by Marge. In order to put an end to Bart's paranoia, Marge decides to take Bart to Springfield Penitentary to show him that Sideshow Bob remains in jail. Bart and Marge see Sideshow Bob in his cell, wearing a straitjacket and writing "Bart Will Die" all over the walls with a pen held in his teeth, which satisfies Bart for the moment.

Marge and Bart return home, and Walt asks Bart if he would go with him to see a baseball game, as the Isotopes are playing the Spokane Cascades. Bart accepts the invitation and they start driving to the game. When Walt doesn't make the turn off of the freeway to Springfield Stadium, Bart suspects that something's up. Then Walt says Bart was right all along because he really is Sideshow Bob! To prove it, "Walt" takes off his shoes and unfolds his long feet, revealing himself to be Sideshow Bob.

Meanwhile, "Sideshow Bob" escapes from prison (by spitting his pen into the guard's eye, grabbing the guard's taser in his teeth, and stunning the guard) and goes to the Simpsons' house. After Marge soaks him with a hose and Homer closes a window on him, "Bob" tells them that he's really Walt. As proof Walt shows them his short feet, and then takes them into Bob's house and shows them pictures of Bart with knives in them, photos of Bart being hanged (and drowned) in effigy, and so on. Lisa finds a picture of The Five Corners, the only point in the U.S.A. where five states meet, with the handwritten notation "kill Bart here." Walt and the Simpsons then head for Five Corners.

Sideshow Bob tells Bart how he escaped from prison: He had heard that prisoners convicted of minor offenses were going to be released, and his cellmate Walt was a minor offender and fortuitously had the same build and facial structure as he did. Just before the release took place, Bob knocked Walt out, switched their faces (doing facial transplant surgery right there in the cell), and then simply walked out posing as Walt when the minor offenders were set free. He then used the proceeds from Walt's investments (which had done very well during his incarceration) to buy the house next door to the Simpsons.

Bob and Bart stop at a diner, and a waitress falls for Sideshow Bob as Walt. She removes what she thinks is a loose thread on his jacket, but it's really one of the stiches from the face transplant. All of the sutures come undone, revealing that his face has been sewn on. Sideshow Bob then runs away, taking Bart with him. Shortly after this, the Simpson family and Walt arrive at the diner, describe Sideshow Bob to the waitress, and ask her where they went. She tells them that Sideshow Bob was headed for Mexico, and accidentally unmasks Walt as also having a sewn-on, transplanted face. The Simpsons believe her and go to Mexico, but Walt, sensing that the waitress is attracted to Bob, knows this is not true and heads for Five Corners instead.

Sideshow Bob arrives at The Five Corners and has himself and Bart stand in two of the states at the meeting point. Then he tells Bart of his plan to kill him: Bob will stand in one state; reach into another and shoot his gun; and have the bullet riccochet and travel through two other states before it finally kills Bart, who will stand in the last state. Since no single portion of the sequence is illegal, none of the five states will be able to prosecute him for Bart's murder. Bart jumps to a different state, forcing Bob to also move to a different state to preserve his plan. Bart and Bob repeat this several times, and Bob becomes frustrated enough that he's on the verge of just shooting Bart and getting it done with, regardless of jurisdiction.

Walt arrives in the nick of time and and takes the gun from Sideshow Bob. Walt unfortunately has a bee under Bob's transplanted face, which distracts Walt and leaves Sideshow Bob an opening to take the gun back. Chief Wiggum then arrives with other cops from Springfield's state to arrest Bob, revealing that Bart wasn't really convinced that Bob was really Walt. After Bart alerted them before he left with Bob, the police then were able to track them because Bob's car is a Hybrid, and all Hybrids are secretly monitored by the government. Bob compliments Wiggum, before jumping to another state (and out of Wiggum's jurisdiction). However, law enforcement officials from the other four states arrive, cutting off Sideshow Bob's escape. Bob is arrested and taken away, and the Simpsons return from Mexico, where Homer has been having misadventures such as arguing with a cook over "How do you say 'taco' in Mexican?"

Back in the Simpsons' neighborhood, Walt's former house is vacant, but only temporarily. A distant Flanders relative moves into the house, and he and Ned start a conversation laced with "Flanders-isms," talking to each other from across the Simpsons' front yard, to Homer's dismay.