A few of my favourites are:
1) "Where are we now".... I always reply "Dont know, cant see the road signs from here".
2) You serve the pax there meal & there's always one that says "do you have it without the sauce"
3) Which is the ladies toilet ?
But my ultimate favourite which always makes me chuckle is when pax open the cupbard where we keep our bags & jackets, turn round & stare at you & simply say " Toilet "
