In which TV series is Walter White a main character?

Who played Serena van der Woodsen in 'Gossip Girl'? Who played Michael Westen in 'Burn Notice'? Who played Carly Shay in 'iCarly'? Who played Alex Russo in 'Wizards of Waverly Place'? Who played Skyler White in 'Breaking Bad'? In which TV series is Skyler White a main character? Who played Hank Schrader in 'Breaking Bad'? In which TV series is Hank Schrader a main character?