Pros
Petco is a fun atmosphere to work in if you like animals and don't mind not getting paid very much. Although most of your time will be spent doing remidial tasks around the store, you do have the oppurtunity to interact with many different animals. Petco does offer a 20% discount to their employees, so this helps if you are a pet hobbyist.
Cons
Petco does not pay well or treat their employees well. Don't expect to be respected or treated like anything more than a grunt. Petco does not foster new ideas from employees. Petco also has a lot of mottos that are very untrue, i.e. "Animals come first". If you are in management, don't expect any help or direction from upper or middle management, their job is to tear you down no matter how good your store looks. They also provide very poor feedback, many times leaving you without knowing what you are supposed to do.