Smile HD is a mature parody animation made by Mister Davie (credited in the video as "Dave Davey") on YouTube on the 24th of August, 2013 based on a remix to the song "Smile" from MLP. It features the main six in which - during a day out - Pinkie Pie becomes violent and proceeds to torment her friends in a gory fashion. Unlike a similar animations from the same user, this is not based on an existing Creepypasta.
The original video was removed because of its violent content and receiving a copyright strike from Hasbro. That being said, there is an 8K video left uncensored posted by another user on YouTube on the 22ndJuly 2020, 7 years after its initial upload.