I wonder if I'm reading these threads too much, because I had a Yotsuba&! related dream last night. I distinctly remember being on /a/ and started reading a chapter called "Yotsuba & Idol...something", and it was a splash page like this >>280273423 and it was a shot from above of Yotsuba, Ena, Miura and a couple of nameless characters on a stage in idol costumes (nothing lewd, pretty modest).
The first few panels of the chapter for some reason had Yotsuba in a dinosaur costume like pic attached, pushing a tiny shopping cart and walking with Ena and Miura. I remember one of the panels had Yotsuba happy and Miura annoyed for some reason. I think I woke up not long after.
I'm guessing the costume part came from the Halloween chapter and the idol part because it's just a thing in anime.