This has been done once by every sitcom and sitcom-like cartoon since 1952.
Alice and Bob are neighbors, and they hate each other. One day, Alice goes to a government office and finds a city map that shows her property extends well past the fence between them. Alice will begin commandeering anything of Bob's that falls into their property. A tree, a workshed, the TV in his living room, etc.
The episode frequently ends with Bob discovering that the first read it wrong, and what it really meant was that the property line cuts into Alice's property instead. Insert defeated "wah-wah-waaaah" trombone sounds here.
This is usually Snapbacked as it never comes up again.
Note that this is a classic example of Hollywood Law: in reality this kind of discrepancy would (1) immediately lead to a lawsuit, which (2) would almost always be solved by somehow granting Bob the land he thought was his. (The mechanisms here are adverse possession, which is basically a Statute of Limitations as applied to property law, if he or his predecessors in interestnote used the land consistently enough for long enough, and various kinds of easements and forced sales if he hasn't.)
- 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.
- The Oscar-winning silent 1952 short Neighbours, directed by Norman McLaren for 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.
- In the classic Polish comedy Sami Swoji two families end up in a Feuding Families situation because a Kargul plowed '3-fingers-width' deep into land claimed by the Pawlaks. The eldest Pawlak son retaliates by hitting the Kargul with a scythe and then flees to America. Decades later the two families need to cooperate to survive the aftermath of World War 2 but the patriarchs still occasionally break the peace when they get into silly property disputes over things like who owns the cat that hunts the rats in their sheds.
- Older Than Feudalism: The Bible prohibits moving your neighbor's boundary stone or other property marker, presumably to prevent just such a quarrel taking place.
"Remove not the ancient landmark, which thy fathers have set." (Proverbs 22:28)
- Subverted in the famous Robert Frost poem, Mending Wall. It isn't necessarily about the property line intruding on either person's side of the fence, but rather whether or not a literal stone wall is needed to solidify the property line.
- Married... with Children: In one episode, Jefferson D'Arcy takes an apple that fell from the Bundys' tree and Al argues with him over the apple's ownership. It leads the two families into finding out the official boundary between their lands isn't even a straight line. The tree belongs to the D'Arcys. The Bundys further research the map and find out the D'Arcys' barbecue drill is in their property. The D'Arcys retaliate by setting a toll booth at the Bundys' garage entrance. The Bundys retaliate by reporting an irregular improvement that, since it's done on what turned out to be D'Arcy property, the D'Arcys are fined for it. They eventually decide to make peace but then another apple falls off the tree and Al and Jefferson fight over it.
- 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.
- The Bonzo Dog Band's song My Pink Half Of the Drainpipe explores this concept in song.
- In a second-season episode of The Flintstones, Barney painted a property line through the middle of the room Fred just added to his house (tricking Barney into doing all the work, of course.)
- The Jetsons: This was the central plot point of the episode "Private Property"; Mr. Spacely had George examine the blueprints, where he believed that Cogswell's new building was 6 inches over Spacely's property line, until Cogswell re-examines the blueprints and finds that his property is the bigger one and Spacely's building was 6 inches over. Cogswell manages to talk Spacely into buying Cogswell's building, which George discovers is 6 inches too tall and has to be dismantled, only to find out that Spacely got stuck buying Cogswell's building which has to be torn down.
- Goof Troop, In the episode "Goof Under My Roof" plays it straight, when it looks like Pete owns half of Goofy's house, and he then claims everything in that half as his. At the end, it turns out that Pete doesn't own half of Goofy's property,. but rather Goofy owns half of his.
- A Mighty Mouse cartoon "The Green Line" featured a town where mice lived on one side of said line, cats on the other. An evil cat spirit tries to get the cats to ignore the line and attack the mice, but Mighty quickly arrives to restore peace.
- One episode of The Pink Panther ("Pink Panzer") 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.