Hands up, you two! Actually, this is the same person. Sylar is just a part of Parkman on season four of Heroes.
Parkman and Sylar - who are really the same person - run in to trouble during the Heroes episode "Shadowboxing."
As Claire's roommate and friend, Gretchen has received a lot of season four air time. Heroes fans are split on how they feel about that.

Heroes Season 4 Episode 8 Quotes

Lydia: It sounds like the Claire Bennet recruitment is a lost cause.
Samuel: You know me. I'm the patron saint of lost causes.

Sylar: I don't get to fly very often, you know. Especially not first class.
Matt: Well, I'm glad my life savings could broaden your horizons.