Flanking (aka "fake planking") is the art of doing a plank, putting the picture of said plank in Photoshop, and using an elementary understanding of the program to create a plank of epic proportions. Sure, we made this up. But if taking pictures of people laying face down and motionless can take the world by storm, imagine what spiffier pictures will do?
King cobra flank
As for planking, further research has clued me into its origins. While it's widely held that the fad was started almost 15 years back by a couple British dudes, the Alibi unearthed the fact that it was actually started by the mighty elephant seal, which spends the majority of its life planking. ... Although they could be a little more creative with it: