The SnO.C. - S2-E5
Continuity mistake: In Series 2, Episode 'The SnOC', we see Zach punching Seth with his right fist. However, when Summer gives him some ice, he covers his left fist with it (which is now bruised and swollen).
Continuity mistake: At the beginning, Kate's friend gives her ex-fiance's letter to Kate. The letter is held differently in consecutive shots.