Clear out a corner Office for the Britcom's creators, Ricky Gervais and Stephen Merchant their new BBC2 series, Extras, is being coproduced by HBO and will debut stateside on the cable giant. (Overseas, the six-episode first season will begin airing this summer; a U.S. premiere has yet to be announced.) In the laffer, Gervais plays a bitter aspiring actor (there's another kind?) and Merchant is his agent. Already lined up to make cameos are Ben Stiller, Samuel L. Jackson, Kate Winslet and, judging from his conspicuous absence today, I'd say Mike Ausiello.