The Cavity Creeps are the main antagonists from an old Crest commercial.
They are a race of evil, tooth-hating creatures at war with an army of children who wish to make the world a better place for teeth. When the Cavity Creep scouts see that the children are not using their usual Crest to power their shields, the Cavity Creeps decide to attack. Unfortunately, the kids are using a new, more powerful Crest toothpaste, and defeat the Cavity Creeps.
The Cavity Creeps have also appeared in pop culture. In the South Park Imagination Land Trilogy, The Cavity Creeps are shown as powerful soldiers of the army of evil. They also appeared in one of Family Guy's cut-away gags, where it is revealed that Peter was once a Cavity Creep.