The first and only time we get to see just what the Spark compartments of Generation 1 Megatron and Beast Wars Megatron look like from the inside. The latter has a vicious-looking spiked tentacle protecting his Spark, while his namesake has a simple, but still crude mechanism covering his.
For whatever reason, the head of Optimus Prime looks much different than previously. It is less blocky, and more rounded, akin to the first episodes of The Transformers (1984). It is easy to miss, since we only get to see him for a moment.