Surprise!

[Five_Inch_Heels]

Thirty-ish couple is looking to expand their experiences. One such attempt leads them to a club, maybe an adult theater. As they're getting into the mood and looking around they see other couple doing things, so they get busy with each other. They're approached by an extremely attractive brunette who just happens to be topless, but is wearing a short skirt. They watch in amazement as the brunette casually keels between the husband's legs and goes down on him for a few minutes before moving to the wife. The couple comments on how wonderful it feels and how much oral talent is at play. Laid back and in near bliss with her legs splayed open, the wife feels the brunette moving up her body, pressing their breasts together and begin kissing her very deeply and passionately. The wife is clearly enjoying tasting her own juices.

Suddenly, she feels a rather impressive cock pushing into her.

 

[liliput1]

I know all there is to know about the crying game
Don't want no more of the crying game

(I assume in retrospect the club name is a giveaway but they were too naive to pick up on it?)

 

[Carnevil9]

I recall a series of short pornos based on this idea, only it was single guys picking up "women" at a bar. I think it was called "Shemale Surprise" or something like that.

 

[Rob_Royale]

I did a couple with a futa story and I made sure to include the husbands realization that the penis didn't eclipse his attraction to the futa. By the end they were all enjoying every bit of one another. I would include that in this idea.