I use the pet zapper2 and my dear pet turned very ugly...is there any way to undo?

no, you cannot 'undo' it.

however you could always use an elixir or potion to change your pet into something else, or continue zapping until you get something desirable.

I used common potion but nothing happened D:

that's because your pet was already a common experiment, you'll have to use something different to change it. like a which will also change it's species.

ah, I see. thanks for the help :> but I haven't found anywhere some kind of paralix elixir :/

And plenty more I'm not bothered to post.

ok thanks ^^