'Boxtrolls' DVD: Tricks are key

However painstakingly arduous you might think animating the 3-D puppets of The Boxtrolls was, the truth is probably much worse.

The latest LAIKA Studios animated feature arrives on Blu-ray and DVD Jan. 20 — and digital HD Dec. 23, right in time for Christmas — and one of the bonus features focuses on "replacement animation," a little trick filmmakers and puppeteers used to make everybody's lives happier and more efficient.

This exclusive clip shows how stop-motion animators were able to work so well with the little creatures in boxes, who raised the little boy Eggs (voiced by Isaac Hempstead Wright) as one of their own and then help him save the town of Cheesebridge from a crazy exterminator (Ben Kingsley). Filmmakers used interchangeable faces for each character, but because the trolls' faces were sometimes obscured by their boxes, an elaborate system of half-heads was developed.

Further complicating matters was the fact that the Boxtrolls' eyes lit up, looking like little fireflies in the darkness. To fix the glowing-peepers problem, they soldered wires to magnets and when each of the replacement faces were put on the heads, the lights would come on.

Other extras for the home-video release include six preliminary animatic sequences, a behind-the-scenes documentary on voice casting, character design and prop creation, a variety of featurettes and a commentary with directors Anthony Stacchi and Graham Annable.