When Larry and Alan are discussing the pumpkin drop tradition, Alan's bag in one shot has a black shoulder strap, and in the next has a gray strap.
When Larry and Alan are discussing the pumpkin drop tradition, Alan isn't wearing glasses in one shot, then when he turns around to run down the steps in the next shot, he is wearing them.
David Sinclair says "...Krugerrands, pure gold able to exchange anywhere and are untraceable". A Krugerrand is one troy ounce (31.1035 g or 91.67%) gold and 8.33% (2.826 g) copper,a total weight of 1.0909 troy ounces (33.93 g) they are made that way to be more durable.
There is no way they're dropping frozen pumpkins off the tallest building of the school without notice, and with people directly below. Hitting someone with one could cause serious injuries and/or fatalities. Larry holding his backpack over his head and walking directly beneath them is ludicrous.
The effects of tear gas usually subside around 30 minutes after exposure, while Don and Gary seem to be able to see and talk perfectly fine after a few seconds. However, as noted in the trivia section, these canisters had CS printed on them. CS gas is a weaker version of tear gas, used in the military for training to give soldiers the experience of tear gas. So Don and Gary would recover much more quickly than from standard tear gas.