what do u fantasise

my boyfriend told me the other day hes love to see a women in her underwear get on a bike,take off the seat and sit down on it,hes been trying to look on the internet but cant find nothing of the sort,i think this is a bit srange,and imbarrassing,iv done the vibrator thing,so would any girls do this for your man,or lads what else do u fantasise about except threesomes!