Certainly done it myself on numerous occasions on the 757 and 737 - sometimes you just need to get the job done. Amazing what can be achieved with a smile and a few bottles of water or soft drinks from the bar to keep up the spirits of the baggage handlers - lets be honest, who would want to do that job every day ?
Helping the cabin crew prep the aircraft, giving a hand to the engineers, manual loadsheets because the agents computer is broken, talking to the passengers face to face.....whats the problem as long as all your own duties are done and dusted ?