1. Cross-dressing
In our days, it 
became common to wear customs in Purim. Obviously there is no Mitzva or 
Minhag involved in this. It is just a folklore --of dubious origin 
though-- that became accepted in Jewish communities all over the world, 
especially for children. We must avoid however, and warn against, cross-dressing in Purim. It is an explicit prohibition of the Tora, Debarim 22:5: "A woman must not wear men's clothing, nor a man wear women's clothing, for haShem your God detests anyone who does this".
 If man dresses to look as a woman, wearing a skirt, or a wig, or using 
make up, etc... or if a girl dresses to look as a man, they are 
transgressing a serious Biblical prohibition. This prohibition applies 
even when one dresses to look as the other gender 'for fun' (R Obadia 
Yosef, Taz, Bakh and others) .
2. Alcohol-consumption
In Purim,today, we participate in a Se'uda, a 
festive meal of Purim. It is customary to serve alcohol, but it is NOT 
permitted to drink in excess. Purim should not be used as an excuse for 
drunkenness."In these days," declares Rabbi Weinreb from NCSY, a leading
 Orthodox Organization in America "when so many of our young people are 
prone to experimentation with dangerous substances, it behooves us to 
warn against the dangers of alcohol, especially on Purim". Quoting from 
Mishna Berura (sec. 695) on the laws governing the Purim SEUDA, the 
festive meal, Rabbi Weinreb emphasized that we are not commanded to 
become drunk, to look foolish and to lose self-control; rather, he said,
 we are commanded to become joyous" in a manner that results in love of 
God and thankfulness for God's miracles."
(See here the other Mitzvot of Purim)
READ THIS IMPORTANT LETTER from Rabbi Avraham Nissanian on alcohol and Purim
