How I can design a grog using metacreator?
It seems suitable to companion and magi creation.
What is the problem?
You can define a Metacreator character as a Grog easily. I don't recall the Metacreator's rules checks specific for Grogs (like Virtues and Flaws). But even if they are not applied, you simply could do that by hand.
Cheers
Took screenshots from my copy of metacreator to show the way to tell it to make a grog.