Topaz is a GUN agent and the human partner of Rouge the Bat. Though at first the regimental Topaz disapproves of the scheming Rouge (who keeps calling her an old lady), the two become friends fast. Their main assignments involved striking at Dr. Eggman and retrieving the Chaos Emeralds, as well as serving as envoys between Sonic and his friends and the government. She is voiced by Kayzie Rogers in the English version and by Yukari Hikida in the Japanese version.
Topaz also seems to have romantic inclination towards Chris Thorndyke's butler, Mr. Tanaka. The two have worked together on several occasions, and when Topaz lost in a tournament over the red Chaos Emerald, Tanaka gave her a necklace, a sign of a growing relationship between them.
Topaz's last appearance was when Sonic and his friends were returning home. She said farewell to her partner Rouge, who gave her a ring as a goodbye gift. This is quite unusual, as Rouge usually covets any jewel she comes across.
Topaz still makes a few appearances in the Sonic X comic book, being once again, Rouge's partner, and their relationship is the same as in the show.