In the scene where Peter is changing into his dress clothes to go see Mary Jane's play, he looks into the mirror. At the first close shot of the mirror, the tickets are blurred because Peter is in focus, but the tickets are clearly on the left side of the mirror. When it cuts to a side shot, if you look, the tickets are now on the right side of the mirror. Then when it cuts close again, the tickets are back on the left side, and Peter takes them off.