Watch this video and afterward read the rest of description of it below. Whatever you do, don't ever try this yourself!
Here is the comment from the video's producers:
You didn't really think that we would take a risk like that right before leaving on our roadtrip? Maybe we would do it for real after the trip, but not before!
"Of course we didn't really have Brandon lie under the RV -- here's a look at how we actually did it. Brandon used Adobe After Effects CS5 to composite the two elements together.
"Basically, for the time that the two elements are intersecting, both the guy on the ground and the RV need to be rotoscoped using Rotobrush in separate layers. After the elements are isolated, they are layered so that the RV is on top of the roto'd guy. All that remains is adding the shadow that passes over the guy. Duplicate the layer of the guy, apply curves to darken the guy to make it look like he's under the RV, then animate a large feathered mask to pass over it at the same rate as the RV."