As did I (along with few Czech animations too) and my child also. I love the Polish stop animation a bit more than the Japanese cartoon, which I've watched also because my child grew up with it but the Polish one that I watched when I was a child always has a nostalgic feeling in it. It's scarier and perhaps a bit more true to the original Tove Jansson stories.

And what do you know, yesterday I tied to find a short story of the Moomin that has the Groke in it and couldn't find a good one but now I stumbled to this one immediately and I didn't even have the Groke in the search words.