Whe Timmy travels into the past, Sheldon is revealed to have been Mr. Turner's rival since childhood, who won Mrs. Turner's affections first and dated her up until college, when he suddenly dumped her after becoming rich, and Mr. Turner then won over his soon to be wife by mopping up her tears. Mr. Dinkleberg became rich because the scientists and military men attending Mr. Crocker's speech were more interested in Sheldon's parachute pants. Sheldon Dinkleberg moved into the house neighboring the Turner's shortly before Timmy was born, and managed to get their nicer house at a better price than Mr. Turner.
Timmy's disastrous ability at a game of charades with his family competing against the Dinkleberg's results in Mr. Turner losing all of his trophies to his hated enemy, causing Timmy to get yelled at and eventually wish for no sound. At the end of the episode, Mr. Dinkleberg gloats to Mr. Turner that he had all the trophies melted into a toilet seat, causing Mr. Turner to scream in rage.
Timmy messing up his dad's office after an errant wish causes Mr. Turner to lose the cleanest office award to Mr. Dinkleberg. Further punishment was given to Timmy when Vicky tricked Mr. Turner into thinking his son had written "My Parents Stink" and "Dinkleberg Rulez" on the wall. When Timmy brought a rocket launcher back from a television show he had wished himself into, it fired and blew up the roof of the Turner's house, at the same moment Mr. Turner's boss was walking by, and the boss immediately awarded a "cleanest house" award meant for Mr. Turner to Mr. Dinkleberg, who used it to play fetch with his dog, which causes Mr. Turner to scream in rage and pull all of his hair out.
Mr. Turner becomes obsessed with proving Mr. Dinkleberg is evil, and employs a variety of spy methods in order to get evidence of evil doing, mainly by sending Timmy to do all the work. Timmy becomes convinced that Mr. Dinkleberg is a good neighbor, and Mr. Turner panics and begins to think Dinkleberg brainwashed his family. He goes into Dinkleberg's house alone, but eventually gives himself away to Dinkleberg, who is hospitable to Mr. Turner at first. Sheldon soon reveals however that he is "really evil" and traps Mr. Turner in his lair. Timmy goes to save his father, and manages to free him long enough for Mr. Turner to panic and run away. While he and Timmy are alone, Dinkleberg reveals that he is not really evil, but wanted Mr. Turner to think so to be happy. This episode also reveals that Mr. Dinkleberg has donated a kidney to Mr. Turner to save his life, and paid over $30,000 for his fake evil lair.