They're decendants of warriors from KISSteria, who locked the Destroyer in a volcano. Like their ancestors, they're sworn to protect the Rock of KISSteria from being found by the Crimson Witch, the Destroyer's creator, and releasing the monster again. They then (somehow) became the biggest rock band on planet, Earth. A cover story was made, where they received the Rock of KISSteria as a gift from Detroit, under the name of "Detroit Rock". They even had an amusement park made after them, where the Rock of KISSteria was kept on display at the Hall of KISStory, until it got to Halloween, and they take it on tour with them.
What's New, Scooby-Doo?
They were hired to perform at a costume party in Banning Junction on Halloween Night. When the Ghost of Hank Banning showed up at the party, they indirectly helped save the day by continuing to play and providing inspiring fighting music for the gang.