Aoi Yuki was offered the role of Tooru to help her cheer up after Puella Magi Madoka Magica and while starring in Gosick.
Satou is an Older Expy of Housaka from Minami-Ke.
Run is an alien.She doesn't tan or even get sunburned, for one thing. And her Ahoge is an obvious antenna. She isn't stupid, just unfamiliar with human customs. Her home planet has lower gravity than Earth, which is why she occasionally leans over railings too far and almost falls.
Kitou is Tooru's mom.She looks a lot like her, and she (Kitou) told her that she (Tooru) always helps her, but maybe it also means that she helps her at home, too.
Tooru is abused at home.
Yuuko is an alternate version of Mio
Run was trying to tell Tooru something when she took her to that "Toy store".