Derpy Hooves is a tragic case of a background pony. She was born with a rare eye disorder that screws up her vision and makes her look…well, “derpy”. This combined with her clumsiness made her the target of vicious bullying that has continued all the way up to adulthood. Her desperate desire to have a friend led to playing “Spot the Derpy”, where in the show she uses her unique appearance to stand out hoping the audience will notice her and be her friend. Eventually though, Derpy grows tired of the bullshit and naturally chooses to get revenge against those who made her life hell, one way or another.
 
As Dark Foam, Derpy uses her sweet, happy-go-lucky nature to make ponies relax and trust her. Failing that, she has the power to create bubbles that hold a variety of effects; she can either use them as a form of mind control to make ponies be her friend forever and ever. Or make them go through the worst nightmares imaginable by inflicting her own suffering upon them and make it ten times worse. Her paper bag attire is a symbol of Derpy’s status as an outcast and a scapegoat for when something goes wrong.