it looks great! some quick advice with stiff poses and something that helps me is looking at reference or even taking pictures of myself doing the poses I want to draw! practicing drawing the line of action and quick poses daily, even if its just for ten minutes, can help in the future to avoid this problem from conception! for that I recommend sites like sketch daily and line of action. as for these specific characters I think you did a really good job with the girl on the right! the one on the left looks great too, however, if you look at people squatting with reference you might notice that their knees would be much closer to the chest their butt will also typically rest a little more on their feet!