Petsburg is a city that's connected to Petropolis by a railroad. It could be possible that the city is in Pennsylvania, considering it's a parody of a city that is located there. The city's train station was, however, the only thing seen of the city. It only appeared in Guard Dog. In A Doomed Christmas, it was shown that T.U.F.F. has a transportation tube leading to Petsburg. This tube may have been installed between the events of Guard Dog and A Doomed Christmas to save hassle.
- Petsburg is an allusion to the real-life city of Pittsburgh, Pennsylvania.
- Kitty, Dudley, and The Chameleon don't seem to use the transportation tube in Guard Dog. This could have saved them a lot of trouble if they used it because they wouldn't have had to ride the train there. It may have been installed between the events of Guard Dog and A Doomed Christmas for this reason.
- D.O.O.M., Bird Brain, and The Chameleon played softball there in Top Dog.
- In Frisky Business, one of Peg's suitcases has "Pets-Burg" tagged on it.