deus ex machina

/ˌˈdeɪəs ˈɛks ˌmɑkənə/

In a movie, when the plot is really complex and then something ridiculous comes in at the end and solves everything, that ridiculous thing is a deus ex machina, an unlikely solution to an impossible situation.

Deus ex machina is Latin for “god from a machine,” and comes from Greek plays where actors playing gods would descend from above and tidy up the mess that humans made. For example, in the play Medea, the title character kills a king, a princess, and her own two children, and just before being captured, her grandfather enters on a golden chariot pulled by dragons and rescues her. It's a narrow escape that only a deus ex machina could provide.

Definitions of deus ex machina

1. noun

   any active agent who appears unexpectedly to solve an insoluble difficulty
   type of:

   causal agency, causal agent, cause

   any entity that produces an effect or is responsible for events or results