I'm waiting on my schematic to finish and I had an odd question..does it make a whole new pet or can I use it like a potion on an existing pet?

I probably should know the answer to this but it's escaping me at the moment..

You can use it on an existing pet. I did!

Thank goodness.

Thanks for the answer, I really appreciate it. :)

When you turn the schematic in with the key, you're given the option of giving a new name or a name of one of your existing pets. The main difference is that a new-built pet gets a cogwheel instead of a gender. Pets that started out something else keep their original gender after conversion. New-built pets that get elixired lose their cogwheel.