I also heard they have even more characters in Japan, such as Grippatchi.
Where did you hear of this information? Back in 2010, previews of the Gotchi Figures were shown at the New York Toy Fair. 14 Gotchi Figures were showcased, 12 of which have been released now. Two figures were shown that to this day haven't been released (were most likely either discontinued or were going to be in Wave 3). These figures were of Grippatchi and Mamametchi. Is it possible that these are the figures you are referring to? I do know that the Tama-Go was released in Asia, so there is a chance that more Gotchi Figures were released, but wouldn't we know of this?