Who played Seth Cohen in 'The O.C.'?

Who played Tobias Fünke in 'Arrested Development'? 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 Marissa Cooper 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?