A large number of character models, documents and pictures from different Lego System characters and models were sent to the developers, who eventually chose to use the Castle, Space, Adventurers and Pirates themes in the game. High Voltage Software chose the characters they liked best from these themes and created character studies for them to "capture the mood of each persona". Certain characters would assume the role of bosses, while others were featured as less skilled opponents. The developers also created two original characters, Rocket Racer and Veronica Voltage.