You don’t have to build Gunpla for very long before you’ll inevitably encounter a Bear’gguy. Heck, all you have to do is simply search for Gunpla online and you’ll probably find one.
I’m not an expert by any stretch, so my information is probably wrong, but as far as I can tell the original Bear’gguy appeared in Model Suit Gunpla Builders Beginning G, an OVA from the early 2000’s that was a sort of precursor to Gundam Build Fighters. The Bear’gguy was a highly modified version of the Acguy, made to resemble a teddy bear. The original is … not exactly adorable, but you get the idea (side note - the idea of making ita bear in the first place seems to stem from the fact that the Acguy is the butt of many fan jokes due to its “cute” design compared to other mobile suits).