anime cameos in lucky star

I have some lucky star on DVD and while watching it, I noticed some familiar looking girls in the backgrounds of episodes 13 and 20. I saw, compiled, and cicled mikuru asahina from the melancholy of haruhi suzumiya and kotori otonashi and yukiho hagiwara from THE iDOLM@STER. I think I saw some K-on! cameos in the opening but I'm not sure. Also, at one point in history I remember seeing rena ryuuguu in lucky star but I can't remember what episode. TT TT If you see her, let me know. I got the screenshots here. [link]

Lucky star belongs to kagami yoshimizu.