As Rachel, Santana, and Kurt are talking the amount, type, and position of pastries in the container between them changes.
In the scene where Sam is about to get his vaccination, the needle in the syringe keeps changing position.
Tina is given white roses, but later has pink roses at prom.
The consistency of the slushee changes from more liquid to more ice.
The rope neither falls nor remains attached to the bucket.
Bree yells at Kitty about not campaigning for prom queen--because the Cheerios need representation on prom court, but two other candidates are Cheerios; it's not as though it all rests on Kitty.