"Cut it out" was a hallmark of the 1984-1991 Nickelodeon TV show Out of Control. The phrase was used often by Dave Coullier (later of Full House fame), and the words were spoken simultaneously with hand gestures:
Cut = scissors motion with the forefinger and middle finger
It = thumbs up
Out = motioning with thumb away from the body
Other memorable parts of Out of Control were the Hurry-Up machine (so you can get your chores over with faster), Ha-Ha (a computer that printed out jokes), and the recurring skits "It's Probably True" and "Great Moments in Inventions".