Eric and Donna trick Hyde, Kelso, Jackie and Fez into eating brownies laced with laxatives. The five each take one, and there is ample brownie left in the pan while it is sitting on the table. However, when Kelso returns to eat another brownie, there is only one left.
At The Hub, the bags of Doritos on the wall at the counter are the modern, foil bags. The bags from the '70s were cellophane with a window.