Use the mosters in the cities listed below to unlock the other monsters. There may be more then one monster to unlock the secret ones. And you might have to re-do the city to unlock the other ones that are in it.

Leon - Play as any starting monster in Las Vegas Kingston - Play as Lizzie in Las Vegas Jack - Play as Harry in Las Vegas Marco - Play as Ralph in San Francisco Shelby - Play as Lizzie in San Francisco Natalie - Play as Marco in San Francisco Kyle - Play as Kingston in London Icky - Play as Ralph in London Edwin - Play as Wally in London Cal - Play as Kyle in Los Angeles Amanda - Play as Kyle in Los Angeles Bart - Play as Kingston in Los Angeles Rojo - Play as Kyle in Chicago Harry - Play as Marco in Chicago Nick - Play as Harry in Chicago Croc - Play as Rojo in Hong Kong Venus - Play as Croc in Hong Kong Jill - Play as Amanda in Hong Kong Wally - Play as Marco in New York Rocky - Play as Cal in New York Joe - Play as Natalie in New York Philbert - Complete all the Par Point Stars in all the cities. Eyegore - Complete all the Challenge Stars in all the cities Bubba - Unlock all the monsters, secret and normal.