During the Christmas Party when David is talking to Carol about being "stitched-up", he makes reference to Series 1 Episode 4, "Training" and his impromptu guitar performance. He says he did a cover of Bob Marley's 'No Woman No Cry', and Oliver, "the office black guy" loved it, but the BBC cut it from the programme... Oliver wasn't in Series 1, he moved from Swindon in Series 2.