The title is play on the chapter titles from the Manga(which is fantastic by the way) The titles always go Yotsuba &...
There are some Azumanga Daioh Diaper artworks up on the internet but no Yotsuba as far as I know.
She's a rambunctious little rugrat isn't she? So its not completely out of the ordinary to see her in this getup is it? Say she meets up with our Sukubo-chan one day and so she is curious about her appearance and decides to imitate her to see if her hair will sprout fire too!
In this pic she is dragging Sukubo around by the arm and showing her new friend off to people! she seems veeerrry excited~