A typical ad would begin with the Cookie Crook attempting to steal the cereal from a live-action breakfast table; often he and the Cookie Cop were portrayed as no larger than mice, so their pictures on the cereal bowl were “life size". The Crook would have some new gadget or scheme to steal the cereal, but then the Cookie Cop would arrive and save the kid’s cereal in the nick of time. Eventually, the format of the ads changed to full animation, and the duo was portrayed as the size of normal humans; a more slapstick approach (similar to Looney Tunes) was used in these commercials.
In 1990, the Cookie Crook was given a sidekick named Chip the Dog. Chip would howl the cereal's name ("Coo-oooooooooookie Crisp!") in each ad before he and his master were inevitably foiled by the Cookie Cop.