Who played Marissa Cooper in 'The O.C.'?

Who played Gob Bluth in 'Arrested Development'? Who played Ryan Atwood in 'The O.C.'? In which TV series is Ryan Atwood a main character? Who played Seth Cohen in 'The O.C.'? Who played Charlie Harper in 'Two and a Half Men'? Who played Alan Harper in 'Two and a Half Men'? In which TV series is Alan Harper a main character? Who played Tony DiNozzo in 'NCIS'?