Dee Dee Planet

ChuChu Rocket! is an action puzzle game. The basic rules of the game require the player to guide mice, dubbed "ChuChus", into a rocket while evading them from dangerous cats, dubbed "KapuKapus". A brief premise is provided in the instruction manual, explaining that ChuChus are living on a space port that is invaded by KapuKapus one day.

In their frantic state, the ChuChus begin running around in chaos, and so the player must guide them to their rockets to save them. Both ChuChus and KapuKapus run in a straight line, and turn right when they hit walls. A player can place up, down, left, and right arrows on the field of play, redirecting characters that step on them. Up to three arrows can be placed by a player at any time; placing a fourth arrow will make the player's oldest arrow vanish, and all arrows fade away over time.

ChuChu Rocket! was developed by Sonic Team. Director and producer Yuji Naka conceived the game as a way to use the power of the Dreamcast to create 100 sprites moving at once. He believed there are two trends to use evolving hardware: one is to make increasingly beautiful graphics, while the other is to squeeze as much processing power to use it to its fullest; he chose the latter in this case.

Naka and his team found difficulty working on the networking component, but believed it was a good learning experience. 's purpose was to test the capabilities of online multiplayer gaming on the Dreamcast; the team used what they learned to help drive the development of Phantasy Star Online (2000). A NAOMI arcade version of the game was also planned, but later scrapped.

The Dreamcast version of ChuChu Rocket! received highly positive reviews. Critics highlighted the multiplayer modes as being great fun and addictive. , and praised it for being easy to pick up and put down.

He concluded the game was "shamelessly retro and monstrously addictive." Other critics also picked up on the game's Japanese and retro aesthetics, citing the simple, cute, and kawaii graphics. Some reviewers drew attention to the game's "chaos" and "insanity", such as Nick Jones writing for Arcade, who said the game was "complete madness and rates as an example of Japanese gaming eccentricity at its very finest". In addition critics also praised the game for its low retail price, giving a great fresh experience to gamers on a budget.

A follow-up to ChuChu Rocket!, Dee Dee Planet, was in development and scheduled for release on the Dreamcast in 2001. The game similarly focused on online multiplayer with gameplay similar to the Worms series. It was reportedly cancelled due to the bugs and problems with its network play. In 2021, a near-complete beta copy of the game was obtained and leaked onto the internet. Fans eventually fixed the bugs, making it completely playable online the following year.

In the GameCube versions of Phantasy Star Online Episode I & II (2002) and Billy Hatcher and the Giant Egg (2003), a limited version of the Game Boy Advance port can be unlocked and played via the GameCube – Game Boy Advance link cable. Minigames inspired by ChuChu Rocket! were included in Sega Superstars (2004) and Sega Superstars Tennis (2008). ChuBei, Chuih, ChuPea, and ChuBach are also playable characters in Sonic & Sega All-Stars Racing and Sega Heroes.