Like other cultural variants, tastes in companion animals (pets) can shift rapidly. An analysis of American Kennel Club puppy registrations from 1946 through 2003 (N = 48,598,233 puppy registrations) identified rapid but transient large-scale increases in the popularity of specific dog breeds. Nine breeds of dogs showed particularly pronounced booms and busts in popularity. On average, the increase (boom) phase in these breeds lasted 14 years, during which time annual new registrations increased 3,200%. Equally steep decreases in registrations for the breeds immediately followed these jumps in popularity. The existence of extreme fluctuations in preferences for dog breeds has implications for understanding changes in attitudes toward companion animals, veterinary epidemiology, and canine evolution.