The Five Obstructions (Danish: De fem benspænd) is a 2003 Danish film by Lars von Trier and Jørgen Leth. The film is a documentary, but incorporates lengthy sections of experimental films produced by the filmmakers. The premise is that Lars von Trier has created a challenge for his friend and mentor, Jørgen Leth, another filmmaker. Von Trier's favourite film is Leth's The Perfect Human (1967). Von Trier gives Leth the task of remaking The Perfect Human five times, each time with a different 'obstruction' (or obstacle) given by von Trier.[1]
For Obstruction No.4 - Leth must remake the film as a cartoon. He does so with the aid of Bob Sabiston, a specialist in rotoscoping, who creates animated versions of shots from the previous films. As such the final product is technically an animation but not a cartoon. Nevertheless von Trier considers the task to be completed successfully.
http://en.wikipedia.org/wiki/The_Five_Obstructions