Go ask Hop

Bonus: the story of the shoes and the fire

Steve:
What clothes: In his underwear
"Hey assholes, you go get some wood, I'll light it up later after we've unpacked." Steve yelled to Dustin and Lucas before turning back to Nancy and Jonathan to unpack the drinks and food. Half an hour later they had a decent fire and a nice pile of wood to make sure it kept burning. Just as Steve was about to add more wood to the fire, he toppled over (don't do the alcohols, kids) and stepped into the fire. His pants and shirt immediately caught fire and he quickly raced to the lake, jumped in, and spent the rest of the night in his, slightly soaked, underwear.
Where: In the woods
I'm sure that, by now, we all know that, with these people, everything always gets out of hand. So, naturally, they all decided to play hide an seek in the forest. Only problem is that, during the game, some people passed out (it was like 5 am and they'd all had alcohol) so they ended up passed out in the middle of the woods, in a place that they, while drunk, considered good hiding places.

Eleven:
What clothes: Nancy's dress
"So it's kind of like spin the bottle but instead of kissing you trade one piece of clothing. It's fun, really." Who else could've come up with an amazing idea like that than Steve Harrington himself (with some help from Dustin). Eleven, who was obviously still slightly new to, well, all of this, had no idea what the fuck that meant. After trading jeans with Mike behind some bushes, it was her turn to spin. And that's the story of how she ended up in Nancy's dress and Nancy, who had already collected Steve's jacket when she told him she was cold and Jonathan's shirt in an earlier round, gave her dress for another shirt.
Where: Piece of wood in the middle of the lake
Because of: Mike and Lexi
It was around 4.30 am by the time that hide and seek really got out of hand and the hiding spots were getting more and more ridiculous. El had already floated Dustin into a tree and by now, Lexi had reached the island on a piece of wood, before it floated away. Eleven, the seeker that round, took Mike's advice (she'd already found him) and grabbed a piece of wood to get to the island. Halfway there she started thinking about other things (mostly waffles) and fell asleep in the middle of the lake, leaving a hysterically laughing Mike on the shore.

Dustin:
What clothes: Dressed
If there's one thing Dustin is good at, it's figuring out exactly how not to have to participate in games he made up. One of those games was the variation on spin the bottle that they were playing. How, no one knows, but Dustin managed to not switch a single item of clothing.
Where: In a tree
Because of: Eleven
"Fifteen!" Lucas called, face still to a tree. Dustin shot one last pleading look to Eleven, who he'd been trying to get to put him in a tree, before she gave up and stuffed him in a tree. Unfortunately, this made it so that she didn't have enough time to find a hiding place and Lucas found her almost immediately.

Lucas:
What clothes: In his underwear (+mustache)
"Lucas, you lost man, I can't make it anything else, buddy." Dustin said, pulling out a sharpie. "Don't 'buddy' me. Also I didn't lose, Will did." Lucas argued. The kids were sat in a circle playing cards while the teens talked by the fire. "I didn't, you did." Will shot back. "Okay, before you guys start fighting let's just make both jump into the lake-" Mike was got off by Will's protests. "let me finish. We'll also draw a mustache on Lucas."
Where: In the forest
Who with: Will
"Lucas why the fuck are you here." Will whisper-shouted through the darkness. "This is a free country, now be quiet before El finds us. She already has Mike."
"I think she's going for Lexi now so we should be good. Now be quiet before we get caught." Will waited a few seconds before calling his name again. "Lucas, did you fall asleep?"

Will:
What clothes: In his underwear (but near Mike's and El's pants)
Now we already know how Will ended up in just his underwear, but the pants are interesting. It was shortly after they'd started playing hide and seek. Mike and Eleven were in the same hiding spot, just a few yards from where Will and Lucas would end up, when they realized there were fire ants and ran away, tugging off their pants as they went since they were full of the insects.
Where: In the forest
Who with: Lucas
We already know this one for the most part. But after Lucas fell asleep, Will sat down with his back against a tree and slowly dozed off, making him fall to the side so he was fully on the floor.

Nancy:
What clothes: Jonathan's shirt+Steve's jacket=skirt and El's shirt
We've already heard this one but just to recap. "Whoa, hey, Nance, you're shivering." Steve said, scooting closer to his girlfriend. "Yeah it is kinda cold." She replied, shrugging. "Doesn't really matter tho-" before she could finish her sentence, Steve's jacket was already over her shoulders.

"Okay, Nance, you start." Dustin instructed, nodding in her direction. She sighed before spinning the bottle, relieved that it ended on Jonathan. They'd seen each other naked before anyways. The rest of the game didn't go so well for her as she also swapped shirts with Henry and gave her dress to El.
Where: In the forest
"'Let's play hide and seek.' They said. 'It'll be fun.' They said." Nancy mumbled to herself while pulling a pile of leaves over her. She quickly remembered that leaves were full of spiders and was about to leave when she passed out.

Lexi:
What clothes: Dressed
Lexi, like Dustin, managed to somehow hack the system and remain dressed for the entire night. Neither of them ever told us how they did it. (By now there are many theories.)
Where: Island
So you know how you should never let midnight decisions lead you to places? Lexi didn't. So, around 4.30 am, it seemed like a good idea to hide from El on the island. That was, at least, until the piece of wood that she'd used to get to the island floated away. Leaving her stranded. There was an attempt at resque, but El fell asleep halfway across the lake.

Jonathan:
What clothes: Tanktop w/flowers (Nancy's) and jeans
Naturally Nancy wasn't the only person he switched clothes with but Mike and Henry made him give them their clothes back.
Where: In the forest
Sometimes, you just wanna hug the earth. And when you're drunk, sometimes you actually do (and bruise some stuff in the process).

Mike:
What clothes: Dressed (minus pants (and shoes obvi))
Like Henry, he made people give him back his clothes. (He lost his pants in the Fire Ant Incident (or FAI) which has gone down in the group's history as the second time Mike ever danced). The shoes are what's interesting. Now obviously they all have keys to their own houses, so around 1 am, they thought it would be funny to go past their houses and drop off their shoes. Anyone outside around that time in Hawkins, must've had quite a weird experience as there were ten kids/teens drunkenly walking through town while trying to be quiet.
Where: On the shore
Well I mean he wasn't just gonna leave his girlfriend behind. Even if she was passed out on a piece of wood.

Henry:
What clothes: Dressed
Henry, like Mike, didn't manage to avoid getting changed during the game. However, when, during hide and seek, he'd found someone that was wearing something of his, he'd change it back and that way he ended up in his own clothes, well, minus the shoes, of course.
Where: In Nancy's bed
By the time that 4 am rolled around, Henry was done. He'd fallen in the lake, out of trees, nearly into the fire. He just wanted to sleep, no offense to the others, but this just wasn't his scene. So when they all went by the houses to drop off their shoes, he remembered where the Wheeler house was and, around 4.30 am, when people were preoccupied with hide and seek and Lexi being stuck on the island, he walked there, snuck into the most accessible bedroom window (Nancy's) and went to bed.