Loosely based on William Joyce's children's book "The Leaf Men and the Brave Good Bugs". Like Rise of the Guardians (2012), it was based on a story told to the author's daughter. This film's protagonist, MK (Mary Katherine), is named for Joyce's daughter, who died of a brain tumor on 11 May 2010 when she was 18 years old.
Over one million hours of work were performed in the production of this film.
The film earned $268 million on a $93 million budget.
The Leaf Men were modeled after Samurai.
The piece of paper that is seen just before the scrolling part of the closing credits has the date, 5-24-13 written on it, which was also Epic's release date.