Jesse is a large dragon resembling Funtime Freddy and is the persona of the user who goes by the same name. He has shown to be able to breathe fire, like you would expect due to him being a dragon, and considers himself a sociopath with mental disorders including but not limited to autism and some form of dissociative disorder. He also has no issue at all with devouring people whole because he's a kinky bastard.
Jesse is the admin of the OC Jess, and interpretations of Withered Golden Freddy/Kenny Bishop, Foxy/Terrance Bishop, Bonnie, Freddy Fazbear/Jeremy Fitzgerald, and has a design for his interpretation of Mike Schmidt, not that he uses the thing, though.
His 'In-Universe' backstory is that he apparently is from a distant planet of dragons like himself, where there is no form of ruler, government etc and the way of life is 'eat or be eaten'.