There are a couple of types of exercise ball that a guinea pig can use as guinea pig toys. However, only one makes one of the best guinea pig toys available especially for those that are in need of guinea pig exercise toys. The other is thought now to be dangerous for guinea pigs to use and those are the ones that guinea pigs can run around inside. These are sometimes referred to as guinea pig exercise wheels. Exercise balls can also be free standing that guinea pigs can be put in unlike the traditional exercise wheels.\r