Harlem Shake FAIL is PewDiePie's take on the Harlem Shake craze of 2013. It is fairly unique in that the only participants are Pewds himself, morphed with multiple filmed characters.
We see Pewds moving around the room as the music starts; he puts on a hat and stands in the center of the room as the music changes. Next scene, we see Pewdie in four different incarnations of himself (thanks to multiple recording sessions and digital splicing): three in three corners of the room, and the fourth in the center, wearing a bra and panties and doing the pelvic thrust whilst waving his arms over his head. The song stops with the growl and all the Pewdies looking off to the side in horror, and we see Marzia glaring at Pewds with a barely contained grin (as presumably the underwear Pewdie was wearing is hers), and finally Pewdie finishes with "Oh Shit!"