Eros

Eros is a planet where, according to Mr. Popo, an evil dragon surfaced before moving on to destroy an entire galaxy. It is likely that this planet had a set of Dragon Balls and over used them, thus triggering their side effects and releasing a Shadow Dragon.

Trivia

 * Eros is a Greek word for love (in this particular case, physical love). This was also the name of the love deity.