The batteries and upgrades for the original Ugobe 'classic' Pleos can work in all versions of the Ugobe Pleo, just not in the Pleo RB (in the same way, never use upgrades designed for the Pleo RB in a Ugobe Pleo).
You can, however, use most of the skits and personalities in both the Ugobe Pleo and the Pleo RB. The ones that don't work tend to be ones that rely on touching the sensors, as some of those on the Pleo RB are different from the ones on the Ugobe Pleo.
If you want to use any of the Ugobe Pleo upgrades, it's a good idea to work out which version your Pleo is already on, and the upgrades work best if gone through sequentially, though you can always change back if you don't like the upgraded version.
I hope that helps.
