As the Glee kids perform and Sue first looks into the teachers' lounge, Emma appears to be walking back to her place after putting money in the jar. In the next shot we see a close-up of the jar and Emma's hand putting a bill in it, then walk back again and high-five Will on the way.
As Coach Bieste watches Artie walking, the sign on the wall next to her says "Glee Club Rocks" but half of the music notes are drawn backwards.