I have two ideas for stories (warning: both are NSFW) One: Applejack is having a lousy time at the Grand Galloping Gala with absolutely no one buying her treats. But then her one customer, that drop-dead handsome Wonderbolt, comes back...
Two: The CMC win a trip to a private island and they bring along Spike. Three gorgeous girls and an alpha male dragon on a remote island with no supervision at all; surely this won't result in anything lewd.

I'd go with idea one in terms of it being the better nsfw story