The movie is based on the series of comic books where Scott Pilgrim ( Michael Cera ) has to defeat the seven evil exs of the girl of his dreams , Ramona Flowers ( Mary Elizabeth Winstead ) to win her heart . The film is about Scott Pilgrim ( Michael Cera ) , a young Canadian musician , meeting the girl of his dreams , Ramona Flowers ( Mary Elizabeth Winstead ) , an American delivery girl . In order to win Ramona , Scott learns that he must defeat Ramona 's `` seven evil exes '' , who are coming to kill him .