When Sam begins flossing her terrible father's toes, she and Freddy have a lap full of push pins ("they're colorful and pointy!"). When they stand up, the push pins are nowhere to be seen.
When Freddy is drinking a smoothie, the lid and straw go from being on the table, to being back on the drink, to disappearing altogether.
At the beginning of the episode. The announcer on the PA at the school says "all girls attending the dance must submit their medical records to the school nurse". Schools do not require medical records for a dance.