Animating a complex metamorphosis effect in clay can be an epic task. Try animating it backwards and reversing it in post production. Start with your final sculpture and animate it transforming into a blob or simple shape. Then export your frames in reverse or flip your animation in editing. This method will give you greater control over the final appearance of the character, and will go a whole lot faster than forming a detailed character one frame at a time. Lots more details in the above tutorial.