io9 had picked up an internet report that it could be Alan Tudyk, but Entertainment Weekly’s Michael Ausiello may be discounting that rumour. While he didn’t didn’t say if the current rumor was true he did say…

Trust me, you do not want to know who’s been cast in this role. Knowledge of this person’s identity will ruin a major Alpha-related twist that Dollhouse boss Joss Whedon has been desperately trying to keep a lid on. Loosely translated into riddle form: What if we were to meet Alpha without knowing we were meeting Alpha?

Whedon also said in a TV Guide interview Alpha may not appear until the 13th episode.