The video, which you can view in full on Youtube, shows just a flash of the Hatter around the 3.37 mark. The screenshot below (thanks, NeoGAF) shows him flanked by two rabbit-masked goons. You can also catch a glimpse of Poison Ivy.
He joins Penguin (voiced by a Cockney-accented Nolan North), the Riddler, the Joker, Bane, Two-Face and Harley Quinn in the game's Batman-villain line-up.
Developer Rocksteady claims we've still only seen a fraction of what Arkham City has to offer - can that really be the case?