Keith (Infinity Apartment)
From Jenny Everywhere Wiki
Keith was a normal human man from one of the universes where the Infinity Apartment existed. He was a neighbour of Jenny Everywhere, and refused to believe her about the Apartment's multi-dimensional nature until, after inviting him over, she opened the door again only for it to now exit to Jenny's front door in a universe populated by Dragons instead of Keith's own homeworld.
He later started hanging around in the Apartment frequently, now aware of its true nature. He once observed Jenny listening at the door of an as-yet-unclaimed room within the Apartment, with Jenny explaining more of the Apartment's functions to him in answer to his question about what she was doing. (COMIC: Infinity Apartment)