If playing Veronica Mars for three years didn't solidify her placement at the center of the geek universe, then this surely will: Kristen Bell will appear on NBC's Heroes this fall for a multi-episode arc. With ''Veronica'' behind her, the fan favorite tells us about her upcoming Comic-Con-friendly roles in ''Heroes,'' and the movies ''Fanboys'' and Judd Apatow's ''Forgetting Sarah Marshall'' -- plus one on ''Lost'' that got away