I have already written five Divrei Torah for Purim so I will take a slightly different approach, weaving together the Parashah Tetzaveh, the special Shabbat of Zachor Et Asher Asa Amalek, and the holiday of Purim (and perhaps a little of Taanit Esther, but the original three day one that happened during Passover the year prior to the Original Purim and not the military fast that we actually commemorate the anniversary of nowadays).
This week's Torah portion, Tetzaveh, speaks of the costume of both the High Priest and the ordinary priest. It goes into excessive detail on the specifics of each piece of clothing, dye, metal to exact specifications of God. These uniforms are meant to identify these holy people and act as a conduit to God.
We don't give clothing enough credit for its importance. It has acted as a catylist device in many historical (read: biblical) events. Clothing, dictated through many changing fashions, comes to symbolize moods and elegance, beauty and care. This is very true in the story of Purim. Sackcloth (a wikipedia article that I must remember to edit) was the preferred form of clothing for mourning in the ancient times (I will be wearing a sack of rice for my megillah reading on Purim where Mordechai dons sackcloth). Mordechai, Esther, and all the Jews put on sackcloth during the three days of their fast to mourn the evil decree of genocide written against them by the wicked Haman. Mordechai is unable to access places he is usually able to enter due to his clothing choice, signifying that sackcloth is not considered acceptable in society. At the end of the three days, an unwashed and unfed Queen Esther removes her sackcloth (and ashes) washes herself and dons the most beautiful clothing and finds favor in the eyes of her husband the King.
Midrashically, Ahasuerus, at the seven day feast which followed the 180 day free-for-all, was dressed in the garb of the High Priest of despoiled Jerusalem, the pure gold of the Temple used for profane purposes by the Persian emperor. Mordechai is dressed in the King's coronation robes when led through the streets in a parade led by Haman, and in the end when Mordechai becomes the Prime Minister, when Mordechai was dressed in the blues, whites and purples, and the gold crown of his office, the Jews had light, joy, gladness, and honor.
I was watching Disney's Aladdin (not as much of a kids' movie as you might think) on the car ride back from Palm Springs and I saw a lot of similarities, beyond the Jafar=Haman thing. Aladdin hides his identity of being a street-rat by dressing as a gallant prince, much like Esther hides her identity from the King. Jafar disquises himself as a kindly old man to get Aladdin to do his bidding. Jasmine dresses in burlap robes to sneak out of the palace. Here too we have the parallels in clothing
So we have therefore arrived at the disguise part of the discussion. Clothing does not have to be literal. Amalek is cloaked in stealth and deceit when they attack the stragglers, the weak, the women, the children, and the elderly of Israel from behind. God's role in the story of Purim could also be thought of metaphorically clothing-related. God hides Himself under an invisibility cloak throughout the story, His Name or appellations not mentioned once in the book, but His name can be seen as acronyms multiple times throughout the scroll.
So today we hide our faces on Purim. Esther can be translated as "I will hide" in Hebrew. We hide on Purim just as Esther hid her identity, and just as God hid Himself from the proceedings in Shushan, though it is hinted at that he was there. Our Megillah ends with the final verse, 10:3, but in the Apocrypha (which is not considered canonical in the Hebrew Bible) the book of Esther continues a few more chapters. The very next verse, 10:4 says "Mardocus said, 'God has done these things'." (Assume that Mardocus is Mordechai, Aman is Haman, etc...). God was there, clothed in both glory and invisibility.
So dress up, wear something fun. Who knows? Maybe the king will like what you are wearing so much that he will make you his queen...
A freylichen purim,
PS: BOO Haman!