As mentioned in the Pet Town page, there is a cheat in the Pet Barn. Now, you can try it on your own here! It is rather very simple, and you can amaze your friends on how you did it.
Do you remember that there's a fence in the Pet Barn and it has pets playing in the fence? Well, some people can't go in the fence, but now you can!
1. Go to Pet Town. If you're in Pet Barn already, then go outside.
2. Go inside of Pet Barn.
3. Click at the fence with the pets in it. Ta-da, you went in the play pen!
If you did all the steps correctly, but then you click outside the fence, you go where you clicked. Now you can't go in the play pen anymore!! (Unless you go outside and repeat the steps!)