One of the sages, Rava, said that King Achashverosh made a party for all his officers and servants on the Sabbath day. On this day Jews customarily begin their festive meal with words of Torah and praise to G-d. In contrast, the gentiles begin their meal with words of licentiousness. Thus, for example, at the party King Achashverosh made, the participants were discussing which women were prettier. Some said Median women were prettier and some said Persian. When Achashverosh heard this he said that his wife, Vashti, was neither Median nor Persian, but Babylonian and asked if they wanted to see her beauty. They answered that they did, as long as she appeared before them naked. Vashti did not agree to appear in the nude: “But Queen Vashti refused to come at the king’s command” (Esther 1:12). The scholars asked: Why did Vashti refuse to appear in the nude? When she organized the party she had intended to create an atmosphere of liberty and licentiousness. One of the scholars, Rabbi Yossi son of Chanina, concluded that the angel Gabriel made Vashti grow a tail during the party so that she would be embarrassed to show her body.
The sage Rava noted that King Achashverosh was angry, as is written, “Therefore the king was furious, and his anger burned within him.” Why was King Achashverosh furious and angered by Vashti? Was he so upset simply because Vashti refused to appear in the nude? Due to this question the sage Rava concluded that Vashti reacted haughtily to King Achashverosh’s request that she appear in the nude and she told him “You are as a stable boy compared to my father, the son of Nebuchadnezzar! My father would drink as much as 1000 people and not get drunk, but wine gets you drunk!” This haughty answer from Vashti angered King Achashverosh and his fury burned within him.
(Babylonian Talmud, Tractate Megillah 12b)