Shrek: Hassle at the Castle is a 2D side-scrolling action platformer developed by TOSE Co., Ltd. and published by TDK Mediactive, Inc. for the Game Boy Advance. The story is loosely based on the events of the first Shrek film, with levels taking place in and around key story beats. The game progresses through a linear path of 24 levels, and as Shrek befriends Donkey and saves Princess Fiona these characters become playable at certain points in the game. Also playable is main antagonist Lord Faarquad. The game features an art style that closely mirrors that of the films - aside from the emphasis on giving characters huge heads.
Primary gameplay in Hassle at the Castle consists of basic action platforming across levels themed around locations and events from the film. Peppered throughout the story are more intensely action-focused levels where specific objectives are required to be completed within a certain time limit (such as chasing the Duloc mascot as Shrek, or making the songbird explode as Fiona). In a simple action brawler fashion, the moves in Hassle to the Castle consist of jumping and basic melee attacks. As more enemies are killed a combo bar fills up and, once filled, allows the player to use a scream attack that kills all enemies on the screen. The choosable characters offer slight variety in abilities - Shrek being strong and slow, Donkey quick and weak, and Fiona fast and strong.
Hassle to the Castle also features a single and/or multi-cart multiplayer mode supporting up to four players by link cable. In this mode, players choose between playing as Shrek, Donkey, Fiona, and Lord Faarquad and are pitted against each other in simple brawler style matches. The primary objective is the collection of coins, which are dropped in varying values from the top of the screen. Hitting other characters makes them drop coins, and when time runs out the player who collected the most coins wins.