Ella the helper-monkey is the main villain of the horror movie Monkey Shines. She is a monkey who was subjected to intense experimentation by a rogue scientist named Jeff - who gives her to his former athlete friend, Alan Mann, after he is rendered quadriplegic after being run down by a truck.
Ella begins harmless enough, proving herself to be a clever and loyal companion as well as Alan's aid in a troubling time - however as the movie progresses Ella begins to grow much too close to Alan, becoming almost romantic in nature and displaying behavior far too humanlike for a normal monkey:
Her behavior also becomes vindictive and cruel, even murderous, and she becomes a danger to Alan and those around himself: it is also shown via dream-sequences that Alan and Ella have began to share a strange psychic bond with her beginning to tune into Alan's rage at his condition and the events around himself.
Ella's murder-spree begins when she kills Alan's former girlfriend, who had been cheating on him with his former doctor, by setting their romantic hideaway on fire. Then Ella killed Alan's jealous, overbearing mother, by electrocuting her in the bathtub. Then, Ella killed Jeff, by injecting him with the very syringe of poison he had intended to use on her after becoming aware of her dangerous behavior - she then disables Melanie, Alan's love interest, before trying to light her on fire.
However in the climatic battle Alan is able to trick Ella into cuddling him via playing a tape-recorder with romantic music - when she does so Alan viciously bites Ella in the neck before throwing her away - killing her in the process.