While researching his work I came across this website - http://www.cartoonhalloffame.org/2005/12/iwerks-ub.html and it completely blew me away. The amount of work he was part of and produced in his life astounds me it's completely overwhelming to scroll through. He obviously had to do it to make his living as times were tough during the great depression, when he was completing most of these works but he obviously loved what he did and his body of work proves this.
His filmography includes:
Directing 112! animation shorts/films
Producing 91! animation shorts/films most of which he also directed
He also helped out on the visual effects and worked in the crew on several other film/shorts.
This to me is crazy but it will be a small feet if I can ever compile a list as extensive as that I would be immensely proud of myself, which I'm sure Ub would be if he had the chance to see this list.
He even managed to have enough spare time to draw a self-portrait:
ASIFA - Hollywood Cartoon Hall of Fame(2005) IWERKS, Ub, [online] Available at: http://www.cartoonhalloffame.org/2005/12/iwerks-ub.html [Accessed: Tuesday 17th January 2012]
Google Search (n.d.) Self-Portrait Ub Iwerks. [image online] Available at: http://www.animationarchive.org/publicity/archiveubiwerks.jpg [Accessed: Tuesday 17th January 2012].