Mason Greyback is a character from the Disney Channel show, Wizards of Waverly Place. He is the love interest of Alex Russo, whose boyfriend is also Justin Russo, her brother.
Mason first met Alex in her art class. The two fall for each other right away. They soon become an "art couple", and create a romantic montage. The two soon become a couple.
It is soon revealed that Mason is a werewolf. After he gets bitten by Justin's vampire girlfriend, Juliet Van Heusen, Mason turns into a wolf, and he and Alex can no longer be together.
Alex eventually finds wolf Mason, and restores him back to human. The two go back to dating.
Alex soon decides to drop out of the wizard competition. She is therefore forced to break up with Mason. The two try to make it work as friends, but realize they cannot do it. Alex decides to rejoin the compettion, so there can be a chance that they could be together.
Alex eventually breaks up with Mason, because he didn't trust her, and accused her of cheeting on him. Mason does everything to win her back, and eventually does.
In the series finale, Alex wins the wizard competition, and is able to continue dating Mason.