The "Mannequin Challenge" is a new viral video meme where people freeze in place like mannequins, without camera tricks. Most of the videos use the song "Black Beatles," by Rae Sremmurd. But how did "Black Beatles" become the theme for the Mannequin Challenge?
I've seen articles that suggest that the craze originated from a segment of the original "Black Beatles" video where the band freezes like mannequins, but upon investigation, this seems to be incorrect. There is a live video of the band doing the challenge onstage during the song, but this seems to have been recorded AFTER the challenge started to gain momentum.
It's probably most likely that one of the early versions of the video used that song, and that later versions imitated the early one --that's usually how these viral memes work. When the video of the actual band doing the challenge surfaced, it probably solidified the connection.