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.
The first Blue Sky Studios-produced film to feature a female protagonist, as well as the first theatrical animated film produced and distributed by Twentieth Century Fox to feature one since Anastasia (1997).
The trivia item below may give away important plot points.
Mandrake is easily considered one of the darkest and most evil villains in a Blue Sky Studios film alongside Madame Gasket from Robots (2005), Rudy from Ice Age: Dawn of the Dinosaurs (2009), Nigel the Cockatoo from Rio (2011) and Rio 2 (2014) and Captain Gutt from Ice Age: Continental Drift (2012).