Like the others have said, making it a bit different from the sprite-swap would be good, since Dorumon is my only favorite Digimon I'll give you some ideas. Just so you know the hit sparks are misaligned. Anyways, I don't know much about Digital Battle Spirit, but are there any full spritesheets (walking, running, attacking, etc) related to Dorumon's evolution (Dorugamon, Dorugremon, and Dorugoramon)? Dorumon could evolve into a superior form such as Dorugamon and have totally different abilities, etc. Or are their sprite(s) limited? This way, you could make Dorumon transform into multiple permanent forms during battle. The alternative would be to make an evolution as its special attack such as Dorumon evolves into Dorugoramon and uses its special attack, afterwards de-evolve back into Dorumon again.