Since Vashti's Crime

was being a feminist, it seems fitting that the punishment was a sex-change operation. Esther 2:1:

א אַחַר, הַדְּבָרִים הָאֵלֶּה, כְּשֹׁךְ, חֲמַת הַמֶּלֶךְ אֲחַשְׁוֵרוֹשׁ--זָכַר אֶת-וַשְׁתִּי וְאֵת אֲשֶׁר-עָשָׂתָה, וְאֵת אֲשֶׁר-נִגְזַר עָלֶיהָ.

1 After these things, when the wrath of king Ahasuerus was assuaged, he remembered Vashti, and what she had done, and what was decreed against her.

A hat tip to Yoav ben Tzruya for this particular drasha.