When Peter is in Ireland and meets Caitlín, they pronounce the name as "Kate-Lynn". In some parts of Ireland the name Caitlín is pronounced the same as Kathleen, as it is the Irish version, but in other parts of Ireland such as Dublin it is pronounced "Kate-Lynn". Although seeing as this is set in Cork they probably would pronounce it "Kathleen" or "koit + leen".
Peter Petrelli's passport shown during the opening flashbacks indicates he is female.
When Peter and Adam escape the facility by going through the wall, there is light coming from that part of the wall casting their shadows, indicating that there actually is a doorway there disguised as wall by special FX.