As Puck is singing "Sweet Caroline" to Rachel, they show Brittany sitting in front of Quinn. When the camera zooms in on Rachel, the chair in front of her is empty but as the performance ends, Brittany is shown in her seat again.
When everyone is watching the clock to see if the football players will show, they all turn and look at the door. They hold their stare for a second, then most look away. It cuts to a shot at the door, then goes back to the kids. The exact same clip is repeated, of them looking away.
At the beginning, a hand is filling up what looks like a blackberry slushier. Yet minutes later, when it gets thrown on Finn, it appears no be colourless (no stain on Finn's clothes).
After Quinn and Finn have slushies thrown on them by the football team, one of the players walking past slips on the slushies on the floor and falls over. Quinn smiles and extras in the background start laughing.