The Weird Who Lives In The Attic is the Mansion official Weirdo from the Weirdo Guild. He always has a hand-puppet named Fontod who has his own voice.
Fontod is a hand-puppet on the Weirdo's right hand that speaks. The Weirdo did not acquire Fontod during his time at the Weirdo Academy(?), but after his assignment to the Mansion. He won Fantod in a skipjack game in Bascomp, on the way to the Mansion (as noted here).
Fontod has no resemblance to any particular species. He has a bow-tie like the Weirdo, a long nose and two downward-hanging ears. He has two arms, most likely the thumb and little finger of the Weirdo.
It is currently unknown whether Fontod is a truly indepentdent entity or a expression of the Weirdo's craft or something inbetween. It may be that the Weirdo is a ventriloquist and was inspired by the puppet he won to be a last-minute addition to his Weirdoing. However, Fontod speaks to the Weirdo addressing him as another person, even when nobody else is around. Fontod speaks coherently when the Weirdo is drunk or half-asleep.
The exact functions of a Weirdo are unknown. He may do the human equivalent of Finangling, helping the various residents of the Mansion in various odd ways.
WARNING MINOR SPOILERS!
The Weirdo also appears to be studying the Mansion itself. He has been known to go through the logs of previous Earls in the Mansion's library. He has also been carefully and covertly observing the Basement and its residents, interacting with them in odd ways (like here in the last strip, where he uses a puppet). He has given a report of his observations to an unofficial visitor from the Weirdo guild to whom he has given a report of his discoveries.