From a clip I can no longer find on YouTube (I think it was there), presumably based on an Earthworm Jim cartoon. Here is Peter Puppy transforming into his monster version.
Traced and colored in Paint Tool SAI.
Pose is traced from a Tekken Blood Vengeance screenshot. Updates were made to make the character look more like his Tekken 5 version rather than the movie version. This draft is unfinished shading.
I need a break and sometimes doing so along with checking over the progress of the work helps think of ways to improve.