The robot donkey is a Boston Dynamics 'Big Dog'. The company was owned by Google when the movie was made.
The tag that Ernest places on the machine with his name also contains a radio frequency in the 10-meter ham radio band and a ham radio callsign, KC4TVZ. In the real world, this callsign belongs to a notorious "lid", or poor radio operator, who likes to hang out on the 10-meter ham band.
In the United Kingdom the film has been renamed "Bad Land: Road To Fury".
The rifle/shotgun that many characters use in the film appears to be a fusion of a Lee-Enfield No. 1 Mark 3 rifle and a Mossberg Maverick 88 shotgun.
Nicholous Hoult & Kodi Smit-McMphee would later reunite in X-Men: Apocalypse (2016)