Dick Harbinger is a police officer obsessed with stopping history from repeating itself. Thirteen years ago, on Halloween, a man wearing a pumpkin head and driving a lawnmower murdered several children. Everyone is a suspect. The school janitor, Zeke, is brought in for questioning. The father of the family is also an obvious suspect and is questioned by police. His daughter, Mary, has caught him on multiple occasions trying to peek at her either while in the shower or while asleep. Mary's friend Rosie is dating Tony "the Schlong" Schlongini, who is the coolest kid in school. He along with many others get killed by Mr. Pumpkinhead.

In the end the detective dresses up as the Lawnmower Killer because no one is taking the threat seriously and he decides to teach them all a lesson. It all started exactly 13 years ago, when Mary Graves' older sister was murdered on Halloween prom night by a power-mowing maniac. Since then, Mary has experienced horror, sexual frustration, even psychoanalysis, but she still sees little lawnmowers everywhere. But tonight will be different. Tonight, at the new Halloween Prom, all the questions of the past 13 years will be answered as the pumpkin headed killer has returned. But hot on their trail is an obsessed cop who won't allow history to repeat itself.

At times Harbinger's family, all sit and eat cake at the dinner table and the slices of cake they enjoy are the size of a dinner plate. Baker also fills his suitcase (which has a tap on it) with coffee and later terminates Harry Vice (Vice principal) who is in charge of the vice. Harry Vice likes to "clamp on down," on student slackers, but he ends up having his head clamped on down in a vice, courtesy of Harbinger.

• Joe Don Baker as Dick Harbinger
• Stella Stevens as Mrs. Doctor Graves
• George Kennedy as Mr. Doctor Graves
• Julia Duffy as Mary Graves
• Scott McGinnis as Norman Bates
• Elizabeth Daily as Bambi
• Michele Tobin as Rosie
• Andrew Dice Clay as Tony Schlongini (credited as Andrew Clay)
• Anthony James as Zeke
• Sonny Carl Davis as The Weirdo (credited as Sonny Davis)
• David Drucker as The Looney
• Jeff Altman as Harry Palms
• Victor Brandt as Dr. Moreau
• Wil Albert as Dr. Denton
• Charles Napier as Chief O'Hara

The film was released theatrically in the United States by Jensen Farley Pictures in January 1983.

Jeremy Wheeler of AllMovie gave the film one out of five stars, and wrote: "Wacko virtually vanished from the face of the earth, which, as it turns out, isn't necessarily a bad thing. For its hundreds of gags and zingers, there are actually very few laughs in a seemingly endless 84-minute running time."^[2] Chris Coffel of Bloody Disgusting praised the film's "frenetic energy" and "killer ensemble cast", writing: "Wacko is not a movie everyone is going to love or even like. Not all the jokes land, and depending on who you ask none of them do. But I can't help but love this movie."^[3]

The film was released on VHS by Vestron Video, and was also released on Laserdisc.

In February 2019, the film was remastered in 4K and released on DVD and Blu-ray by Vinegar Syndrome.^[4]

• Wacko at IMDb  
• Wacko at Rotten Tomatoes
• Wacko at AllMovie