Beast Wars II Powerhug (1998)

While it is true that animal forms have been a part of the Transformers franchise since the very beginning, the transition to the Beast era is marked by a move away from strictly mechanical approximations of animals to more organic forms. A focus exclusively on animals (as was the case when the Beast era began) also meant a wider variety of fauna being represented. It is hard to imagine a Transformer based on a pill bug (called a "roly-poly" when I was growing up) having come out during the "Generation One" era, but by the Beast era, such a mode was by no means unusual.

Smallest Transforming Transformers Bumblebee (2003)

Bumblebee was consistently described and depicted as one of the smallest of the original 1984 Autobots. This, of course, ignored the fact that other Minibots were essentially the same size (especially Cliffjumper, whose mold was so frequently confused with Bumblebee's back then that, as often as not, new Cliffjumper toys are often just straight repaints of Bumblebee toys), and as later explicitly-small Transformers like the Micromasters were introduced, it became a less important aspect of Bumblebee's character as time passed. When the "Smallest Transforming Transformers" Bumblebee toy came out in 2003, it may be seen as a return to Bumblebee's roots, although in fact the other toys in this line were, again, roughly the same size.