Batmanning is an online video and photo fad in which participants hang from an object by their feet, much like a bat, and post the results online. Batmanning is one of a series of Internet memes that involve incongruous or bizarre body positioning, including planking and owling.
Techopedia explains Batmanning
Batmanning appears to have emerged in September 2011, when the UK's Daily Mail reported that the craze was started by students at Purdue University who had been filming themselves in the position since 2008. The students promoted their videos to the online community in 2011, leading to a major spike in online interest. The fad saw a resurgence in August 2012 when it was promoted by Perez Hilton.
Batmanning is similar to a smaller craze called batting, but this older fad appears to differ in that participants hang from their legs, rather than their feet.