That’s usually called a post-credits scene or mid-credits scene if it plays during the credits. If it’s just a short extra clip or joke at the end, people also call it a stinger or credit cookie.

Common terms

  • Post-credits scene : shows up after the credits.
  • Mid-credits scene : plays while the credits are still rolling.
  • Stinger / credit cookie : another informal name for the same kind of bonus scene.

Plain-English answer

If you mean “the movie is basically over, but they keep showing edited scenes over the credits,” the safest term is credits scene or post-credits scene.

TL;DR: post-credits scene is the common term, and mid-credits scene is used when it happens before the credits finish.