So in this shot we can see only Rei has a purse:

Later, Usagi is shown to keep the pen in her cleavage: 

So then, where is Ami’s stuff? She doesn’t seem like she’d likely use her boobs as a pocket, and her dress doesn’t give her the same easy access as Usagi’s does anyway. 

The obvious answer is that her stuff must be in Rei’s purse.

And that’s cute enough on it’s own, because that’s such a real detail (back in the days of school dances, I was always the friend with the purse holding everyone’s stuff).

But it also got me thinking: what if Ami and Rei got ready together?

Now, I don’t imagine Usagi would be very patient after she transformed. She’s ready and Rei and Ami look amazing anyway, why do you need to put on tights Rei chan we’re going to be late.

Yet Rei and Ami look very put together. I think after Usagi left the arcade, they sighed and agreed that no matter what Rei said about having a bad feeling, Usagi would end up going to the party. And they would go with her, because god knows Usagi cannot go alone.

So they stop by Ami’s apartment and she grabs an outfit; the closest thing she can find to a party dress is a simple blue oneshe wore last year to watch her mother receive an award for the advancement of medicine, but Rei promises it’s good enough. Then they head to the shrine and Rei picks a dress from the collection of ones her father sent her to wear for dinners with him (which she may or may not have attended) and lets Ami choose from the corresponding jewelry sets. They brush each others hair and awkwardly compliment how each other looks (because they’re beautiful, but neither is used to being opening about such things like Usagi is).

Usagi’s call comes right when they expect it. She doesn’t seem surprised when they show up already dressed to the nines, but maybe she’s just forgotten that they don’t have disguise pens. She slips tiaras into their hair (because of course Usagi has a little collection of tiaras, of course she does) and off they go.