"Support GLaDOS by becoming a Potato and subscribing!" ~ Hoshcof
Potatoes are the name by which Hoshcof calls his fans. The reason why is because in Valve's video game Portal 2 (one of Hoshcof's favorite games), GLaDOS, the antagonist, gets turned into a Potato. From that point on, GLaDOS always says negative things when reflecting on the experience. So when Hoshcof says "Support GLaDOS by becoming a Potato," he means supporting her by going through the experience themselves.
However, Hoshcof realized that GLaDOS and the Potato model were owned by Valve, and if he were to try to make any money from his videos, he'd have to change the phrase and model, so that he wouldn't be sued or lose the ability to monetize his videos. So Hoshcof made a new model himself using a generic Potato image he found online, the "Deal With It" shades, and Burt Reynolds' nose and mustache. He dubbed this new model "PotaDOS", a reference to the old, outdated operating system that started computer gaming, MS-DOS.