I think Slaanesh probably lets people through fairly often, (s)he'd get kind of bored just sitting around with the same sex slaves and food and whatever all the time, as getting through all the trials would be super hard to do. So like once in a while (s)he'd just let some random guy through, he'd be all relieved that he made it though the trials that seemed super easy, and then he'd see her at the other end of some throne room or whatever.
But he's just some random dude that happened to wander in, so even at 100 meters away he already can't resist her, not that anyone else could either. And (s)he obviously has a dick, whether or not you think (s)he's male or female. And from across the room, the guy thinks that yeah it's a bit gay, but it's small and cute, definitely a feminine penis, so it's cool.
Now he's sort of speedwalking to Slaanesh's end of the room, and he realizes that (s)he's not as small and petite as he thought from far away, (s)he's actually around 6'2, not counting the horns. He's a bit troubled maybe, because he's only 5'11.75, but is already in love with Slaanesh so he wouldn't really care. But once he's about 10 meters away and his pants are coming off, he realizes that her dick isn't as small as it seemed either.
Stumbling towards Slaanesh the guy looks down at his dick and back to hers, and realizes that it must be something like 9 or 10 inches, though it is uncut and perfectly smooth, ivory with a slight pink tint to it. He stumbles, his pants are around his feet, and lands on his face. When he looks up, Slaanesh is right above him, and he sees her dick close up finally, it's somewhere between the thickness of one of those thin redbull cans, and a normal pop can, the kind that most people definitely can't fit in their anus. However, it's too late. She's on top of him, and his pants are already down. His anus isn't even self-lubricating, unlike Slaanesh's. And in the end, there's so much blood that Khorne pops a semi.