Sigfriend "Siggy" Manheim is the main antagonist of Brian Henson's TV film Jack and the Beanstalk: the Real Story. He is the man who manages the business affairs of the main character, Jack Robinson (the descendant of the Jack from the original fairy tale), and he encourages him to care only about his business and never get married so that Siggy would inherit the company after Jack died. He keeps the stolen Singing Harp and Goose that Lays the Golden Eggs all to himself. He is portrayed by Jon Voight.

When Jack climbs the beanstalk, Siggy and the others believe he is dead, so Siggy inherits the company. However, he is surprised when he finds out Jack is alive.

At the end of the film, while he attempts to kill the deceased kindly giant Thunderdell's adoptive daughter Ondine, and Jack, the other giants frighten him away.

According to a newspaper headline, due to the public's belief that he has gone insane for claiming that he is being hunted by giants, he is sent to an asylum.