PetVille is rolling out a new way to make a few extra coins in the game -- the Happy Neighborhood bonus. The bonus works like this -- the more neighbors you wash and clean up after, the bigger the bonus you'll be able to collect each day.
Each pets' happiness level will be indicated by an icon (see image below) at the bottom of the screen. The green icon means the pets are happy, the yellow icon less happy and the red means the pet is unhappy. Naturally, that means the more green neighbors you have, the larger the reward. This change is clearly designed to encourage you to get as many friends as possible to play the game, which can be good or bad, depending on how many of your friends are willing to oblige and how many block you for spamming them with yet another game request.