Crossover (fiction)

Ivan Tsarevich and cameo appearances of Pepper and Carrot in episode 4 of Morevna Project

A crossover is the placement of two or more otherwise discrete fictional characters, settings, or universes into the context of a single story. They can arise from legal agreements between the relevant copyright holders (known as intercompany crossovers), common corporate ownership or unofficial efforts by fans.

This is different from a spoof, where one discrete character, setting, or universe, copies another character, setting, or universe, often in a comedic manner.