Nickelodeon's Rugrats must triumph over the greedy Angelica yet again in Rugrats: Castle Capers for Game Boy Advance. Seeking out hidden items and avoiding adversaries, Tommy, Chuckie, Phil and Lil, Kimi, and Baby Dil are the pint-sized stars of this adventure. Stu Pickles has built a castle play set for the Reptar Pizza Chain and Angelica has deemed herself queen of the castle while hiding the babies' things. Playing through six multivariate levels, players help the babies explore the castle to find their missing possessions.

Levels include: Beanstalk Babies, Snow Problem, Ali Baby and the 40 Fleas, Dessert Island, Clock Work Babies, and Sure Would Forest. At the end of each level, players will find one of the six hidden items that Angelica has taken. While searching for the items, such as Dil's binky and Tommy's screwdriver, players will also find food items that can be used to deter enemies such as Squirrels, Dummie Bears, and Cuckoo Birds. Each baby will also encounter the other babies along the way. The character chosen at the beginning of the game will be the only baby players can control, but the others will follow closely behind. Other finds include diapies, coins, and cookies for extra lives.

Each level is composed of both horizontal and vertical action with the babies climbing, toddling, jumping, and flying to make headway. Six different environments are available for play from the beginning, and range from cupcakes, candy, and ice cream in Dessert Island to castles, genies, and cloud mazes in Ali Baby and the 40 Fleas. Once a level is begun it cannot be exited, but when a level is completed, a game-generated password will allow players to return to play with their progress saved. Play begins with 25 tries, but not all hazards or falls will deplete them. After locating all six hidden items, the game is finished, but players can choose to repeat the adventure as a different baby.