Changing the date of the requirement for this meal and for joy, in different types of towns: Megillah 2b
When the requirement applies, if Purim is on Shabbat: Megillah 4b-5a
Having the meal at night, vs. during the day: Megillah 7b Postponing the study of Torah for the Purim meal: Megillah 7b
The Meal Itself
The obligation to drink until one cannot tell the difference between "Cursed is Haman" and "Blessed is Mordechai": Megillah 7b
