Its plot follows a young athlete who becomes a paralyzed quadriplegic, and develops a bond with an intelligent service monkey named "Ella" who becomes homicidal after she is injected with an experimental serum of human brain tissue.

Producers Peter Grunwald and Charles Evans of Orion Pictures acquired the rights to Stewart's novel in 1985, and began production two years later, with Romero assigned to direct.

It had a protracted post-production and editing process, as Romero shot more film than he had on any of his previous projects, particularly due to the use of live monkeys.

His friend, Geoffrey Fisher, suggests he get a Capuchin monkey as a service animal to lift his spirits and help around the house.

Allan dreams of running through the grass at night, and believes he has a telepathic link with Ella, whom he suspects can escape the house.

Allan returns home and tries to mend bridges with his mother, but feels a burst of rage at her utter contempt of Melanie.

When Ella comes near enough, Allan bites her on the neck and slams her body against the back of his wheelchair and into his tape deck, killing her.

[4] Journalist Michael Wilmington notes that the film's thematic weight rests in the presentation of the antagonistic monkey, Ella: "The audience that rejects her as a little toy-terror--or the movie as a piece of icy misanthropy which perversely trashes women, animals and quadraplegics--misses the point.

"[5] United Artists had originally optioned Michael Stewart's novel, Monkey Shines (1983), for a film adaptation in 1984, having purchased the rights for $20,000.

[6] Executive producer Gerald Paonessa commented that he had wanted George A. Romero to direct, as he felt he "had a wonderful, dark sense of humor.

[7] Monkey Shines marked Romero's second feature film produced with a major studio, after 1982's Creepshow, as well as the second most-expensive.

[10] Interiors of Allan's house were constructed by set designer Cletus Anderson, a longtime collaborator of Romero's.

[9] Another issue was the film's overall length, as Romero had completed a very long and involved shooting script that numbered over 240 pages.

The original intended ending of the film was unreleased until 2014, when it was included as a bonus feature on its debut Blu-ray release.

After Allan regains his ability to move on his own, Burbage is assaulted by animal rights protesters who had earlier attacked Geoffrey for experimenting on monkeys.

[12] Several critics praised Monkey Shines for its portrayal of its philosophical themes: David Kehr of the Chicago Tribune heralded it as Romero's "most complex and challenging creations... [Romero's] is a style of philosophical fiction that seems hardly to belong to the 20th Century at all, but rather to the 18th Century school of Swift, Diderot and Voltaire.

Ella, preternaturally sensitive to all her master’s desires, becomes infected with his hatreds--just as, in the lab, she’s been made addicted to a serum containing human brain tissue.

"[5] Richard Harrington of The Washington Post made similar observations about the character dynamic: "Alternating between comfort and revenge, [Ella] seems the ultimate victim, an unwitting pawn.

[6][16] Members of ADAPT formed a picket line in wheelchairs at the Hollywood Pacific Theater the Saturday of the film's opening weekend.

[6] Bill Bolte, a member of Adapt California, commented: "The idea of a monkey attendant turning into a monster is appalling.

"[16] On August 10, Orion Pictures issued a public apology, removing the content from media advertisements for the film, promising to consult disability experts for promotional materials of upcoming projects.

[6] Monkey Shines holds a 53% approval rating on the internet review aggregator Rotten Tomatoes, based on 32 critic reviews, with its consensus reading: "While not one of horror legend George Romero's more evolved efforts, Monkey Shines delivers enough primal fear to satisfy more forgiving genre enthusiasts.

[18] Several parodies exist, some notable examples are: Metro-Goldwyn-Mayer Home Entertainment released the film on DVD on September 28, 1999.