Vin Diesel is a special kind of star — the kind of guy who would post a video on Facebook of himself walking around on stilts. We say that because it's exactly what he did Wednesday morning (October 16), and honestly, we're still trying to figure out what's going on.

On the surface, Diesel is just stomping around the set of "Fast and Furious 7" on stilts. But he's actually preparing to do motion capture for Groot, a sentient tree and one of the members of the "Guardians of the Galaxy," Marvel's sci-fi superhero epic planned for next year. He even meets up with Djimon Hounsou (in "Fast and Furious 7" and "Guardians of the Galaxy" too) to briefly discuss his one-line role. (Groot only ever says "I am Groot.")