Some people confuse Classical Conditioning with Reinforcement Theory. To keep them separated just look for the presence of rewards and punishments. This type of influence is extremely common. Sure, the animals come running even if you are opening a can of green beans. They have associated the sound of the opener with their food.
Classical conditioning works with people, too.
Go to K-Mart and watch what happens when the blue light turns on. Cost conscious shoppers will make a beeline to that table because they associate a good sale with the blue light. And classical conditioning works with advertising. For example, many beer ads promeniently feature attractive young women wearing bikinis. The beer is simply associated with this effect.