Note about Nana Mizuki and Dog Days, and how she's literally all over the shop, singing songs and voicing characters designed for her (oh and Nanami is a blatant expy of herself).
I think Tsuzuki just went,
"Okay, Mizuki-san, thanks for my car, house and fat pay check from Nanoha, I want to make some new anime that all whacky, so what do you want to do with it?"
And so we have Rico and Nanami and singing. All that's missing now is Nanami breaking out into enka and we can call it a Nana-chan idol anime.
