Scene stealer

A scene stealer is a character in a film or dramatic performance that dominates the audience's attention, often through charisma, humour or powerful acting, thus "stealing the scene" or "stealing the show". The term usually (but not always) applies to a supporting character, such as a sidekick, best friend, confidant, villain, etc. Sometimes the term is used for a minor character who has unexpectedly (and perhaps inappropriately) drawn attention away from the star.