Property Line

This has been done once by every Sitcom and sitcom-like cartoon since 1952.

One of a pair of rival neighbors discovers on the city map describing their property that it extends into said rival's. They will begin commandeering anything of the neighbor's that falls into their property. Their tree, workshed, the TV in the their living room, etc.

The episode frequently ends with the rival neighbor discovering that the first read it wrong, and what it really meant was that the property line cuts into the first's property instead. Insert defeated "wah-wah-waaaah" trombone sounds here.

This is usually Snapbacked as it never comes up again.

See also This Is My Side, which is the same plot in miniature. Compare and contrast with Foreigner for a Day.

Examples of Property Line include:

Comic Books

There was once an issue of Disney Magazine that had this happen to Donald Duck. He finds a bricked-up doorway in his cellar, behind which is a chest of valuable antique coins. He sells them, and goes on a spending spree, only to have his neighbour come by with a map proving that anything behind the bricked-up door is actually on his property. All of Donald's fancy new furniture is repossessed, and immediately re-purchased by the neighbour, so Donald has to make do with some old chairs found in the main part of the cellar. Turns out the chairs are even more valuable than the coins were.

Film

The Oscar-winning silent 1952 short Neighbours, by the National Film Board of Canada, is a dramatic and disturbing instance. A surreal anti-war parable, it depicts an escalating battle between two homeowners over the ownership of a single flower growing right on their property line. Watch it here.

Live Action Television

Sanford and Son
Married... with Children
That '70s Show - happened exactly like the trope's definition, starting with Bob taking things from Red's garage and ending with Red finding out that he owns part of Bob's house.
Nickelodeon once had a special Maniac Magee about a town where white people stayed on one side of a boundary, black people on the other, and yet both sides still were able to run their town in a capable manner, (The duality would be resolved by the Fastest? Kid in the World, can't recall how.)

Western Animation

In a second-season episode of The Flintstones, Barney painted a property line through the middle of Fred's house.
The Jetsons
SpongeBob SquarePants did this.
Goof Troop
One episode of The Pink Panther had an unseen narrator building up conflict between the Pink Panther and his neighbor, starting with a couple of borrowed possessions, but then coming into this trope when he, at the narrator's urging, saws off a limb that extends over the line, dropping leaves into his yard. The neighbor retaliates by sawing off part of the Pink Panther's house that was extending into the space over his yard. The narrator gets the panther to build a wall, then the neighbor to bring out a unit of artillery, the panther to bring out something bigger, the neighbor to call in some military help... At the end, the narrator is eventually revealed to be The Devil.