wait, I realized where I got thrown off. I thought you were implying there were talking about a fox, chicken, and satyr form unlockable in a different game. (The pictures from the post above also threw me off.) I'm going to have to go back and find that chicken one.
No worries, you're not missing any forms, I just threw in a few bad ends that are not based on playable forms. The chicken one is pretty easy to find once you know it exist. Probaly something you already guessed but its on the farm.