Gunther is the secondary antagonist of the horror film, The Funhouse.
Against her father's orders, teenager Amy visits a sleazy traveling fun fair with her new boyfriend Buzz, her best friend Liz, and Liz's irresponsible boyfriend, Richie. At the carnival, the four teens smoke marijuana, peep into a 21-and-over strip show, heckle fortune teller Madame Zena, visit the freaks-of-nature exhibit, and view a magic show.
Richie dares the group to spend the night in "The Funhouse" - actually a dark ride. After the park closes, the teenagers settle down inside the ride, at which point they witness the ride assistant - a man in a Frankenstein suit who never speaks - engage Zena as a prostitute. He experiences premature ejaculation, but despite his request Zena won't return her $100 fee. He murders her in a violent rage.
The teenagers try to leave, but find themselves locked inside the ride. As they attempt to escape, Richie secretly steals the money from the safe from which "Frankenstein's monster" took Zena's fee.
The ride's barker, Conrad Straker, discovers what "Frankenstein's monster"—his adopted son Gunther—has done to Zena. Conrad also realizes that the money is missing. Thinking Gunther took it, he attacks him. Gunther's mask is removed revealing a gruesomely deformed face with sharp protruding teeth and ruby-red eyes.
The teens see this, and Conrad realizes someone is watching. He stalks the ride to eliminate any witnesses and heckles Gunther into a murderous rage. Various ride props are used as murder weapons.
The teens die one at a time by the hands of Conrad and Gunther, until only Amy and Buzz remain. Buzz kills Conrad, but is then killed by Gunther. During a showdown between Gunther and Amy in the funhouse's maintenance area, Gunther is electrocuted and crushed to death between two spinning gears.
As dawn breaks, Amy emerges from the funhouse while the animatronic fat lady perched atop the ride laughs.