Shapeshift animation?

Here from a previous post. I want to make an animation that allows my enemy to change their character form (GameObject) and attack the player. Does anyone who's good with animation know how I can do this? If so, I'd greatly appreciate it if you could show me how. Please and thank you!

Thanks in advance!
-D.P.
Here's how I want the animation to look, skip to 5:18 for ending:

 

Nothing happens in that video at the time provided.

 

3:55 sorry

 

@Mecanim-Dev , thanks for the help!