You Owe Me

Some day, and that day may never come, I will call upon you to do a service for me. But until that day, consider this justice a gift on my daughter's wedding day.

—Don Corleone, The Godfather

Buddha, Zeus, God! One of you guys...do something! Help, Satan! You owe me!

—Professor Farnsworth, Futurama

A main or regular character in a really thick mess is helped out by another character, who appears just in the nick of time, clearing up all problems. (A good example of a Deus Ex Machina.)

But what happens now?

Mr. (or Ms.) Helpful may then demand reciprocation, binding the previously helpless character into an undesirable situation.

Almost always accompanied by the phrase "You owe me," or a close variation.

See the other side of this, Makes Us Even.

Examples of You Owe Me include:

Anime and Manga

Misty from the original Pokémon series joined up with Ash's party on the grounds that, after Ash stole and accidentally destroyed her bike, he owed her a new one. "You owe me a bike!" was a short-lived Running Gag, which was ultimately forgotten until the very end of the Johto arc.

Film

Said by Han Solo to Luke in Star Wars after Han saved Luke from becoming a Human Popsicle on Hoth: "That's two you owe me, Junior".
- And inverted in Return of the Jedi when after being rescued, Han doesn't just claim they're even but thanks Luke as follows: "Hey, Luke, thanks for coming after me - now I owe you one."
In Midway, Henry Fonda asked a colleague at Naval Intelligence to help him re-investigate accusations of subversion directed at the family of his son's Japanese-American girlfriend and used this as leverage.
In White Christmas, Danny Kaye's character uses You Owe Me on Bing Crosby's character fairly often. Kaye saved Crosby's life during World War II, at the cost of a broken arm himself and knows that he can use it anytime he wants without ever using it up. He doesn't even have to say the words "You owe me", all he has to do is clutch at his arm.
The Godfather: tradition requires that Don Corleone grant any favor asked of him on his daughter's wedding day. He does so, but reminds the people for whom he does so that they now owe him a favor in return—and what he asks of them will be of at least the same degree of seriousness as what they asked of him. The mortician that Don Corleone helps in the beginning of the novel is eventually called upon to reconstruct the face of Sonny Corleone, one of the Don's sons, after he is savagely murdered.
Highway to Hell (1991): When Royce turns Rachel over to the Hellcop, he says that the Hellcop owes him one. Near the end of the movie, Hellcop is pursuing the protagonists when Royce tries to get in on the action. The Hellcop threatens to shoot him if he interferes, but Royce says "You Owe Me One!"
Subverted in The Beast of War (1998). A Soviet soldier knocks down an Afghan rebel pointing a jezail musket at a fellow soldier and says, "You owe me." The soldier doesn't bother telling him that the Afghan had actually pulled the trigger a moment before, but the weapon had misfired.
Used a little differently in Pitch Black with Johns and Riddick. Johns spares Riddick's life when there was an argument over whether he should live or die and Riddick suggests that killing him is their best option.

*Johns fires at Riddick, who flinches, and his chains drop*
Johns: "I want you to remember this moment. The ways it could have gone, and didn't."
(Riddick grabs Johns' gun and aims at him, ready to fire)
Johns: "Do we have a deal?"
Riddick: "DAMN!" (beat, and he gives Johns back his gun) "I want you to remember this moment."

- Riddick was clearly smart enough to know that Johns thought he could use Riddick in some way. By not killing him, Riddick (in his own personal code, at least) instantly absolved himself of any favours he might owe Johns.

Literature

In Neverwhere this is the Marquis de Carabas' preferred method of payment. This is best exemplified by him giving a minor character a potent magical charm in exchange for a minor service, so that the person will owe him a favor. And also relying on that character overusing the charm so that he'll need the Marquis' help very shortly, thus ensuring that the man will end up owing him an even bigger favor.
Subverted in a Jack Higgins novel. The protagonist (a British officer) tries to play this card to get information from an IRA man whose life he saved in Korea. The IRA man calmly points out that the debt is already paid because he had him in his sights a few months ago and didn't pull the trigger.
The premise of You Owe Me a Murder is Kim agreed to commit a murder on behalf of someone called Nicki, and in exchange Nicki would kill Kim's ex-boyfriend. Kim thought they were joking… and then Kim's ex mysteriously died.

Live-Action TV

Vengeance Unlimited: You can owe a return favor, or you can pay one million dollars. Cash.
This is what the mysterious hero of the show Stingray told anybody he decided to help.
Averted in Oz. An inmate saves Warden Glynn from being stabbed during a Cooldown Hug by surrogate son turned murderer Clayton Hughes, who ends up being stabbed by his own blade. When the inmate tries to cash in on this by asking to become the Warden's receptionist (a privileged position) Glynn angrily sends him back to solitary as his presence would only remind him of Clayton's death.
During an episode in the third season of Buffy the Vampire Slayer, the Mayor and his new Dragon bring in some kind of necromancer demon to remove Angel's soul and bring him over to their side. It seems to work at first, but is later revealed to have been a ruse on Angel's part to get info on the Mayor's plans. The necromancer is shown at the end talking to Giles about now his debt has been repaid by helping with the trick instead of doing what he was hired for. Apparently, Giles introduced him to his wife years ago.
- Averted when Buffy saves a bank manager from a rampaging demon, but he still refuses to give her a loan.
Angel. Apparently the reason why Illyria saved Gunn from the hell dimension. As Angel had just been talking about how Illyria was only staying at Wolfram and Hart because "it reeks of influence", this act has disturbing implications.
A humorous example occurs in NCIS: Los Angeles while Hetty is trying to improve teamwork between Deeks and Kensi by having them waltz. While this is going on, Hetty mentions that she plans to have Callen and Hanna (who are both male) do the same thing later on that day. Then Eric shows up with a case, interrupting the dancing lessons. As the investigators get ready to head out to the crime scene, Eric tells Callen and Hanna that they owe him. They agree.

Tabletop Games

Planescape has a minor faction known as "Ring Givers" who generally get along with other creatures and accumulate favors rather than wealth or other plain forms of power. They have many detractors, but as a rule nobody really wants to mess with them, seeing how they tend to have interesting people who owe them one, including rather powerful "friends" both in low places and in high places.

Video Games

In Fallout: New Vegas, one of the ways you can resolve the situation between the NCR and the Kings is to call in an old favor from The King himself if you've finished a series of quests for him and haven't cashed in the favor yet.
In Atlantica Online, many of the mercenaries you recruit join you after doing them a favor. Leonardo joins you after you rescue his daughter Lisa, Mary Read after you defeat Davy Jones, Odysseus after you help him lead his forces into Troy and so on and so forth.Said "favors" are also tradeable between players.
This is how Dimitri eventually joins the gang in Sly 3: Honor Among Thieves. First, he helps you reunite with Murray in exchange for busting him out of jail. Next, he gives you information in return for owing him a favor, which he calls in a few months later. After you fulfill this favor, however, he sticks around to help rescue Penelope and pull off the Cooper Vault job.
In Valkyria Chronicles II, Anisette can say something along these lines when a character you're controlling (that isn't her) opens fire on an enemy and she is close by.

Western Animation

In Around the World With Timon and Pumba, Pumba roped Timon into doing a good deed by telling him "he owed him one" (complete with a flashback to a Big Damn Heroes moment).
Parodied in Jimmy Two-Shoes. After Jimmy saves Lucius' life, he casually says this trope in a tone that suggests he'll never collect on it. Lucius, however, quickly becomes paranoid that he will and desperately tries to pay him back.
ReBoot has Bob use this trope on Megabyte. Having saved Megabyte in a game, Bob gets Megabyte to let him, Dot and Enzo go at the end of the episode. Having read the appropriate part of the Evil Overlord List, Megabyte remarks that he and Bob are even now so this trope doesn't appear again.