This skeletal-looking creation is a Mack Marble trial truck, and it comes from regular bloggee and TLCB Master MOCer Thirdwigg, who has eschewed his usual all-mechanical approach for a suite of Power Functions electronics. Which means his latest model has done 100% more Elf-smushing than all his others combined.
There are mechanical functions too though, with working suspension and a 5-cylinder piston engine present, and you can check out more of Thirdwigg’s Mack Marble at his Flickr album of the same name.