Well, I have to admit a lot of it was a mystery but here are some information that you might find useful.
http://www.tentonhammer.com/node/65276
http://www.mmorpg.com/gamelist.cfm?g...re=2811&bhcp=1
Kind of went into the mysteries of pet melding too on the first interview. It's possible that your pet mutate into a type that isn't either of the two you meld and change appearance completely. Possible to change into a mob that isn't actually available to catch too. I'll definitely be melding quite a few pets in OB. It's funny how they referred to Pokemon too. :3 Gotta catch em all?