Early on, Jonathan's earring appears in his left, then his right ear, and even both ears.
When Stephanie is first introduced with Kirsten and Pamela, her hair is brown. When Kirsten comments that it's the football player known as # 12, Stephanie's hair is black or raven. When #12 approaches the three girls, Stephanie's hair is brown again.
For the entirety of the diaper commercial flashback, the twins are dressed in the new clothes Betty bought for them. But there is one frame near the beginning of the narrative in the flashback in which they are shown in their "normal" clothes.
When Kirsten, Pamela, and Stephanie split up to search for Tommy, there's a risque moment in which the former two girls' have slight up-skirts, especially Kirsten, and they seem to go commando, not wearing panties.