Based on the popular animated television series Rugrats , Castle Capers follows the story of Angelica, who claims to be the queen of Stu Pickles' castle. She has hidden all the Rugrats' toys inside, and it's up to the player to reclaim them. The game is divided into six side-scrolling levels, each with a unique theme, where the player must navigate through obstacles and enemies while collecting items that Angelica has taken.
The gameplay revolves around exploring the castle and its surroundings, collecting food to divert enemies like squirrels and cuckoo birds, and gathering diapers, coins, and cookies to increase the player's life. The player can choose which Rugrat to play as, but they will encounter the others along the way as non-playable characters (NPCs). The ultimate goal is to finish the game with the chosen Rugrat.