Reversal of Expectations and Norms:
Drinking:
אמר רבי חייא ... נכנס יין יצא סוד
א"ר אילעאי בשלשה דברים אדם ניכר בכוסו ובכיסו ובכעסו ואמרי ליה אף בשחקו:
Costumes:
הַגָּה: ... וּמַה שֶּׁנָּהֲגוּ לִלְבֹּשׁ פַּרְצוּפִים בְּפוּרִים, וְגֶבֶר לוֹבֵשׁ שִׂמְלַת אִשָּׁה וְאִשָּׁה כְּלִי גֶּבֶר, אֵין אִסּוּר בַּדָּבָר מֵאַחֵר שֶׁאֵין מְכַוְּנִין אֶלָּא לְשִׂמְחָה בְּעָלְמָא;
[From Rama's notes on the Shulchan Arukh]
Note:...Regarding our custom to wear costumes on Purim, and for a man to dress in a woman's dress and a woman to wear men's clothing--there is no prohibition on this since their only intent is joy.
Difference: Sinning Before Repentance
(ט) הָאוֹמֵר, אֶחֱטָא וְאָשׁוּב, אֶחֱטָא וְאָשׁוּב, אֵין מַסְפִּיקִין בְּיָדוֹ לַעֲשׂוֹת תְּשׁוּבָה.
(9) One who says: I shall sin and repent, sin and repent, they do not afford him the opportunity to repent. [If one says]: I shall sin and Yom HaKippurim will atone for me, Yom HaKippurim does not effect atonement. For transgressions between man and God Yom HaKippurim effects atonement, but for transgressions between man and his fellow Yom HaKippurim does not effect atonement, until he has pacified his fellow. This was expounded by Rabbi Elazar b. Azariah: “From all your sins before the Lord you shall be clean” (Leviticus 16:30) for transgressions between man and God Yom HaKippurim effects atonement, but for transgressions between man and his fellow Yom HaKippurim does not effect atonement, until he has pacified his fellow.. Rabbi Akiva said: Happy are you, Israel! Who is it before whom you become pure? And who is it that purifies you? Your Father who is in heaven, as it is said: “And I will sprinkle clean water upon you and you shall be clean” (Ezekiel 36:25). And it further says: “O hope (mikveh) of Israel, O Lord” (Jeremiah 17:1--just as a mikveh purifies the unclean, so too does he Holy One, blessed be He, purify Israel.
Difference: Solidarity and Social Justice
(טו) כֵּיצַד חוֹבַת סְעֵדָּה זוֹ. שֶׁיֹּאכַל בָּשָׂר וִיתַקֵּן סְעֵדָּה נָאָה כְּפִי אֲשֶׁר תִּמְצָא יָדוֹ. וְשׁוֹתֶה יַיִן עַד שֶׁיִּשְׁתַּכֵּר וְיֵרָדֵם בְּשִׁכְרוּתוֹ. וְכֵן חַיָּב אָדָם לִשְׁלֹחַ שְׁתֵּי מְנוֹת בָּשָׂר אוֹ שְׁנֵי מִינֵי תַּבְשִׁיל אוֹ שְׁנֵי מִינֵי אֳכָלִין לַחֲבֵרוֹ שֶׁנֶּאֱמַר (אסתר ט יט) "וּמִשְׁלוֹחַ מָנוֹת אִישׁ לְרֵעֵהוּ", שְׁתֵּי מָנוֹת לְאִישׁ אֶחָד. וְכָל הַמַּרְבֶּה לִשְׁלֹחַ לְרֵעִים מְשֻׁבָּח. וְאִם אֵין לוֹ מַחֲלִיף עִם חֲבֵרוֹ זֶה שׁוֹלֵחַ לְזֶה סְעֵדָּתוֹ וְזֶה שׁוֹלֵחַ לְזֶה סְעֵדָּתוֹ כְּדֵי לְקַיֵּם וּמִשְׁלוֹחַ מָנוֹת אִישׁ לְרֵעֵהוּ:
(טז) וְחַיָּב לְחַלֵּק לָעֲנִיִּים בְּיוֹם הַפּוּרִים. אֵין פּוֹחֲתִין מִשְּׁנֵי עֲנִיִּים נוֹתֵן לְכָל אֶחָד מַתָּנָה אַחַת אוֹ מָעוֹת אוֹ מִינֵי תַּבְשִׁיל אוֹ מִינֵי אֳכָלִין שֶׁנֶּאֱמַר (אסתר ט כב) "וּמַתָּנוֹת לָאֶבְיוֹנִים", שְׁתֵּי מַתָּנוֹת לִשְׁנֵי עֲנִיִּים. וְאֵין מְדַקְדְּקִין בִּמְעוֹת פּוּרִים אֶלָּא כָּל הַפּוֹשֵׁט יָדוֹ לִטּל נוֹתְנִין לוֹ. וְאֵין מְשַׁנִּין מָעוֹת פּוּרִים לִצְדָקָה אַחֶרֶת:
(15) 15 How is the obligation of this meal? That one eat meat and prepare as pleasing a meal as his hand can [afford]. And he should drink wine until he becomes intoxicated and falls asleep from his intoxication. And likewise is a person obligated to send two portions of meat or two types of dishes or two types of food to his fellow, as it is stated (Esther 9:22) "and sending portions, one man to another" - two portions to one man. And anyone who increases sending to friends is praiseworthy. And if he has no [means to do this], he should trade with his fellow: This one sends his meal to that one and that one sends his meal to this one - in order to fulfill, "and sending portions, one man to another."
(16) 16 --- We do not [give to] less than two poor people. One gives one gift to each one: Coins or types of dishes or types of food. As it states (Esther 9:22) "and gifts to the destitute" - two gifts to two poor people. ---