During a rehearsal of "Start Me Up/Livin' on a Prayer," the girls turned a microphone stand upside down for Lea Michele to sing into. The microphone fell out and hit Michele in the face.
First appearance of Darren Criss as Blaine Anderson
When Quinn confronts Sam and he slams his locker, the lock mechanism is actually unhooked. This happens with Puck slamming his locker shut, too, when he tells Artie he's skipping town. This might be the only episode in the entire series wherein the padlock on a locker isn't closed.
When Will asks Sue if he heard right that Coach Beiste quit, she calls him "Annie Sullivan" and asks if he needs her to "sign it into [his] palm". This is a faulty reference; the correct one would be Helen Keller. Helen Keller is a famous woman who became both deaf and blind after an illness in infancy. Annie Sullivan was her teacher who taught Helen to communicate using tactile sign language and to read and write Braille.