This sequence of sketches is source I used to create this original transformation design animation:[link]
Like the previous head animation [link]
I used "Morpher" to create the in-between frames. However this was actually the first animation I made using the program, so hadn't worked out all the bugs. You'll notice the transitions are a little more jerky in this. This is because I didn't realize that Morpher defaulted to an "ease-in/ease-out" method of generating the timing, and I didn't catch on until it was finished. Unfortunately, the program was pretty slow, so I didn't bother to re-render the entire affair after I figured it out. I did apply it to the animations I did afterwards, though.
I ultimately refined the design of the final stages, but this served as a useful study.