As Bart and his friends hang out in the tree house, Martin uses a submarine-style periscope to spy on Lisa and her friends, who are having a tea party in Lisa’s bedroom. When Lisa realizes what the boys are up to, she pulls on a string tethered to a tin can used for eavesdropping. The tugging causes the tree house to rock back and forth, until finally, it collapses, sending Bart and the other boys tumbling in every direction. Using stolen railroad ties, Homer vows to build Bart a bigger and better tree house. Marge summons the assistance of some local Amish people, and soon after construction of the spacious structure is complete. The Simpsons host a lavish grand opening of the new space, and people from throughout Springfield are invited to attend. Unfortunately, Homer plays the same jukebox record fifteen times in a row, causing sparks to pour out of the jukebox machine. The tree house catches fire, and guests panic, racing for the exit. Homer becomes trapped under an ice sculpture. Homer calls to Santa’s Little Helper, hoping the dog will help pull him free. Instead, the dog grabs a leg of turkey and runs off. Snowball II rushes into the tree house and, with a swipe of its claws, causes Homer to regain consciousness. Thinking there’s a net below, Homer jumps out of the tree house…only to hit the ground with a thud.

Afterward, Homer lavishes Snowball II with praise, while berating Santa’s Little Helper as cowardly and selfish. A sad Santa’s Little Helper watches as Mayor Quimby renames Springfield Dog Park after Snowball II. And while being interviewed by Kent Brockman on television, Homer claims he doesn’t own a dog. Homer and Marge take Santa’s Little Helper to a pet psychiatrist. He recommends a new role model for the dog. Later, Santa’s Little Helper finds Homer’s Duff bear can and starts drinking from it. A news photographer captures the image. H.K. Duff, the owner of Duff Brewery, sees the picture and becomes inspired. He tells his underlings that Santa’s Little Helper will be the company’s new spokesperson, replacing Duffman. Soon after, the Simpsons confer with H.K. Duff and review the contract he wants them to sign, which states that the dog’s new name will be Suds McDuff. After appearing in a popular television commercial, Santa’s Little Helper becomes an overnight sensation. With sales of Duff beer soaring, H.K. Duff gives Homer wads of cash.

A short time later, the dog’s original owner, Les, crawls out of the woodwork. He claims he’s still the dog’s owner. As proof, he plays news footage of Homer making the claim that he doesn’t have a dog. H.K. Duff takes the wads of cash from Homer. Les exploits the dog at every opportunity, making his life miserable. Bart, Lisa and Marge vow to get their dog back. They approach Duffman at the Springfield Men’s Mission, and lobby him for help. With little to lose, Duffman dons his old costume and promises his support. Later, at the beach, Bart and Lisa outline their plan: Homer will pretend to drown and call the dog’s name. When the cowardly animal doesn’t respond, Duffman will save the day. Unfortunately, when Homer thrashes in the water, he attracts a shark. Fearing for his life, Homer tosses a keg of beer into its mouth. The shark gets drunk, attracting the attention of an appreciative crowd. H.K. Duff proclaims the shark is the company’s new mascot. Les realizes his meal ticket has evaporated, and gladly gives Santa’s Little Helper back to the Simpsons.