The Adventure Time Level Kit features a playable level and offers a Land of Ooo background, multiple stickers, objects and materials as well as various music tracks. It costs $4.99, according to Sony.
Five new Adventure Time character costumes are also available: Finn, Jake, Ice King, Gunter and The Cosmic Owl, which are available for LittleBigPlanet 3 characters Sackboy, Oddsack, Toggle and Swoop. The Adventure Time Costume Pack costs $5.99 with individual costumes priced at $1.99. The costumes are also available for free, as PlayStation Network avatars.
You can read Polygon's review of LittleBigPlanet 3 here.