I helped develop two other ideas in the vein of the Zooble toy line - Monster Masherz and Teensie Titans.
Monster Masherz took the animal transformation of the Zoobles' characters and added an attitude change. Then we took it one step further to apply to the vehicles as well. When the animal drivers transform from cute to brute, the trucks transform into ferocious animal/machine hybrids. When you press/release on the character's head, the face transforms and likewise when you press down on the vehicle. Unfortunately, we only got to develop two of these ideas.
Teensie Titans took a medieval fantasy route. Warriors throughout history battling it out on animals that transform into mythological beasts.
Lion transforms into Griffin.
Bull transforms into Minotaur.
Minotaur reverts back into bull.
Rhino becomes Minotaur.
Snake becomes Dragon.