One of those hijinks got me to thinking. In brief, or something like it: one of the characters, Alice Dice, is a pirate, ruffian, and sex fiend. (Before the campaign started, she'd slept with all the male PCs, and with several important NPCs in the female PCs backstories. Blame the event tables.) Lately, she's been sleeping with Zane Archer/Sir Dave Bowman, space accountant/ship engineer who is terrified of her.
At one point that night, Alice brought a (male) rugby player back to the ship and suggested to Zane that they have a threesome. I'm pretty sure her player (my roommate, incidentally) thought this would be funny, and would freak out Zane, me, and the rest of the table. A typical player antic: she was looking for a reaction.
But Zane turned out to be rather more enthusiastic about the idea than she'd been expecting, which brings me to the point of this story: Game Masters like getting a reaction out of the players just as much as players like freaking out the GM. Now, sure, it fit the character, and I also wanted to make a broader point about the setting and society. But I also knew it'd throw her and the rest of the party for a bit of a loop, especially the player explaining to her that "guys are less open to that than women are." And that's an opportunity too good to pass up.