I always enjoy seeing a range of facial expressions when the quality is good. When the quality is bleh and the faces look retarded, having different facial expressions would probably just worsen everything. However, with Lucky Star, the facial expressions depict their emotions so well, it’s really quite impressive. Tsundere Kagami is a perfect example with her tsun-tsun and dere-dere remarks (lol even if it’s in Kona-chan’s imagination). Kona-chan herself has a variety of expressions, though I find that they are either cute or funny so it’s all good. Oh and she even says ‘uguu’ in this episode (Hirano Aya must’ve had fun)!