Maynard Gabbaline
Maynard Gabbaline is a resident of Teras Terrace who shows up to all sorts of social events despite the fact that he is, at least to the Mongleys, completely indistinguishable from an ordinary stepladder. Actually, saying he "shows up" may be a bit misleading, since he doesn't get there by his own power; another resident always picks him up and gives him a ride. Maynard himself never seems to move, or speak, or do anything at all to demonstrate that he's alive and not just an unremarkable inanimate object.
In spite of this, to the Mongleys' befuddlement, all the other residents of the Terrace treat Maynard as if he's alive, including him in event invitations and in conversations. Of course, he never speaks back or answers any questions asked him, but the Terrace residents insist it would be rude not to talk to him anyway. And, naturally, actually using him as a stepladder would be the height of gaucherie.