In which TV series is Cristina Yang a main character?

In which TV series is Ari Gold a main character? Who played Meredith Grey in 'Grey's Anatomy'? Who played Derek Shepherd in 'Grey's Anatomy'? Who played Cristina Yang in 'Grey's Anatomy'? Who played Miranda Bailey in 'Grey's Anatomy'? Who played Dwight Schrute in 'The Office'? In which TV series is Dwight Schrute a main character? Who played Pam Beesly in 'The Office'?