ART DESIGN:

Katamari’s story, characters, and settings are bizarre and heavily stylized, rarely attempting any semblance of realism (the people, animals, and creatures look like they were carved from milk cartons), though the brands and items used are based on those current in Japan during the game's production.  The graphics are bright, cheerful, and colorful, and in keeping with the game's overall theme.
Takashi felt that by creating subtle elements of the game, such as sound effects when you roll something up, vibration from the controller, and character reactions they were able to express the sense of rolling really well which had a very big effect in adding to the overall feeling of the game.  They made these adjustments to the game design, so it really reflected the uniqueness of rolling the katamari. For example, this game actually does have some combo elements. In fighting games, the combo is usually expressed by a number, but in Katamari Damacy, if you roll up multiple objects in a row, you will see fireworks, confetti, or twinkling stars around the Prince, shown in the bottom right corner of the screen.

Overall, through all the sound effects and colors, a peaceful ambiance of the entire game established. This includes many individual elements, such as the graphic style, the color, the sound and music, the movies and cut-scenes, the incredible zany worlds and the overall theme of recreating the night sky.   Takashi also felt that there was a lot of aggressiveness and violence in current games so what he “tried to do was not only bring peaceful feelings to the game, but also create something totally different, which would be more exiting than just being peaceful.”  Because of the uniqueness of the game, it was natural that the movies, sounds and interface all carry this similar, unique theme.