Another easy trophy to unlock. After you completed the first level for the King of All Cosmos, go back and play it again. When the level is over, you are asked if you want to turn it into a Star or Stardust. Choose Stardust. Quit the level and the trophy will unlock when you're back in the Village Square.
Not entirely sure if it works with the RoboKing levels, but it definitely works for the King of All Cosmos levels.