Is O'Dowd's character really necessary?
I like Chris O'Dowd as an actor a lot, but the more I see of this show the more I think it would be better off without the "imaginary friend" angle. I don't think the quips O'Dowd provides add to the show at all -- the kid and his family are strong enough to carry the show without him. (Plus, he may be getting too old to have an imaginary friend).
(I can imagine somebody who's never seen the show tuning it after the opening titles and being very confused by O'Dowd's presence.)