If you're unaware of Ivanek, I whole-heartedly recommend you catch his performance as lawyer Ray Fiske in the legal drama Damages. He recently won a "Best Supporting Actor" Emmy for his work there, and it was certainly a highlight of the series for me. So rent the DVD, or catch BBC4's repeats every Saturday at 10pm. You may also recognize him as Juliet's husband Edmund from Lost, or Andre Drazen from season 1 of 24.
Ivanek's casting is another coup for the superhero drama, which has always been able to attract a mix of cult favourites (George Takei, Nichelle Nichols, Christopher Ecclestone, Kristen Bell) and respected old-hands (Richard Rowntree, Eric Roberts, Malcolm McDowell, Stephen Tobolowsky, Bruce Boxleitner, Robert Forster). Clearly, everyone's aware it doesn't hurt your career to get your face in something superhero-related; just ask Christian Bale and Robert Downey Jr.