In the movie, Oh and Tip do not get along at first, since Tip believes that the Boov are responsible for abducting her mother. Oh, on the run from the other Boov, convinces Tip to give him a ride in her car in exchange for helping her find her mom. At first, Oh is planning to trick Tip into taking him to Antarctica, away from the other Boov, and even tries to steal her car to do so. Unfortunately for him, Tip catches him, and Oh is forced to comply.
After a while, the two stop being so antagonistic toward one another, and after Tip lets go of her grudge and Oh stops trying to trick her, they start to get along. Tip shows Oh a bunch of things from the human world, which he seems to enjoy. Eventually, they begin to open up and talk about themselves to one another, and realize that they have quite a bit in common: neither of them really fit in with their societies, and they often feel left out.
After a while, Oh starts to show affection for Tip, often turning ink when he thinks or speaks of her (a sign of joy or affection). He even apologizes to Tip for the Boov invasion of Earth, and when the Gorg start to invade, he wants to take Tip onto the Boov ship and save her life (Tip refuses angrily since she has not yet found her mother, leaving Oh quite distraught when he has to leave her behind.) In the end, Tip and Oh work together to stop the Gorg, and the Boov are able to stay on Earth alongside the humans. Tip and Oh become best friends.
Many fans like to continue their relationship after the movie. As with most pairings, some fans interepret their relationship to be platonic, while other see it to be romantic.
Note: Please only add examples that are part of the RotBTD fandom.