Ken could often be found at the 13th St. Barber Shop near WKU where his buddies, Howard Poindexter, Fred Turner, and Slick Thurman cut hair.
In a controversial contest, he edged out Roger Walker of Australia, Paul Grant of Wales and his fellow Pumping Iron co-star, Mike Katz, of the US, to take the first place.
He went on to compete at the professional level the following year in the 1976 Mr. Olympia contest, where he again defeated Mike Katz to win first place in the heavyweight (over 200 pound) division.
Waller is shown as a devious and cunning character who tries to undermine Mike Katz's concentration by hiding his lucky T-shirt, and discussing his plan to do so with fellow bodybuilders Roger Callard and Robby Robinson in one of the film's most memorable and infamous scenes.
Waller had an uncredited, but prominent, cameo in the film Stay Hungry as "Dougie Stewart", the rival of bodybuilder Joe Santo (Arnold Schwarzenegger.)