The wizard had seen this scenario many times before, and likely would many times again. Not to say it wasn't a favorite of his.
But... this might actually be a slightly nice change of pace. In fact, in a way, it was like a fresh summer breeze.
This time the one asking for costumes for their friends October costume party was NOT some sex happy teenager or collage kids who wanted costumes that were all based around 'big busts and round rears', but instead a harmless and innocent little girl who had been given a limit debit card (too young normally to be trusted near one most parents would say) by her mother as she took care of a hair appointment next door and a promise not to go anywhere else.
Her name wasn't Alice, Sabrina, or Dorothy, but Hellen.
His store had no age limits, though there were things even the wizard wouldn't sell to children. But there were things he would.
He did politely inform Hellen that he was a real wizard, and that his costumes would slowly transform the wearers, and ultimately warp reality so they had ALWAYS been those things, and all, including the wearer, would think it normal, sans Hellen herself, since she would be the party's 'host'.
Using a cell phone that again 90% of parents wouldn't let a child of Hellen's age own one, she called her friends.
While the girl did innocently ask her friends 'do you want to become what you described before', her friends, equally innocent, had affirmed that yes, they were what costumes they wanted. So the little girl had innocently come to the conclusion that her friends and classmates wanted to be turned into their costumes, and her little friends had had agreed to a magically binding contract.
The wizard assumed Hellen his costumes were one size fits all.
For the record: just because the costumes would turn into the real thing after being worn, didn't mean the wizard didn't have some personal pride in them functioning as very good costumes with or without the mighty enchantment upon them. Let it never be said he sold sub-standard merchandise.
The costume list was vast and varied. A child sized plastic doll. A two-girl pegasus costume. Dragon girl. Living Ghost. A generic Japanese magical girl (he was no longer allowed to sell copyrighted character costumes). A cute critter costume to serve as a familiar/advisor/mentor. A robot-furry-fox-character. Wild Kitten Anthro. Little Lady Liberty. And that was just the tip of the iceberg with several others on Hellen's list from her classmates. The world would be very different after Hellen's costume party.