Idk if that counts as a crossover but I've been having...
ideas involving Portal (the games) and SSSS...
And they go two ways:
1) What would happen if you took the crew members and stuck them in Chell's position as a test person?
Once you get Lalli to move (the cake lie worked only once), he aces every test. Needs rewards in shape of cookies.
Emil is all hyped about doing cool portal stuff and winning challenges... only to run away screaming from the turrets.
Tuuri finds a screwdriver somewhere, proceeds to open and study the portal gun, the turrets and in the end, GLaDOS as well. She wins the game.
Sigrun argues with GLaDOS to get the hardest puzzles and proceeds to muscle her way through. The turrets are scared of her.
Reynir figures out all the fun stuff with portals. Tends to squeak or yell happily while doing so.
Mikkel sits in a corner and refuses to even look at the portal gun and grumbles about why it had to be a gun. And requiring exact aiming. Why. His superior intellectual tells him exactly how to solve the puzzles... if he could only hit his targets.
Kitty is just herself and tends to climb on GLaDOS. And attack/play-fight turrets.
2) Let me introduce you the concept of the Portal "Long Fall Boots" to the world of SSSS
(watch the trailer for the boots if you don't know how they look or what they do:
Now that you know or if you knew them before... imagine, what if boots similar to these were a thing in SSSS?
Imagine that the Finns (yes, for once it's the Finns being all technical, for plot reasons) developed these boots for scouts and hunters - nokia started out with shoes, getting back to the roots (broots?) is always an option - sometime until Y90 and with the rest of the Nordics not really interested in what the Finns are plotting in their forests, the invention never crossed the border. The SSSS long fall boots enhance running speed, jumping stats and enable safe landing from long jumps, giving scouts and hunters an advantage while running from monsters or scouting an area. They are usually worn when the area is known to be dangerous so they're not a permanent fixture but Lalli is used to having them on here and there.
When Lalli shows up at the pier in the beginning of the story, he doesn't have any Long Fall Boots with him bc they are usually stored in the headquarters for maintenance and only given out when needed. So they start off without them but sometime later in the story Taru manages to get them a pair shipped thanks to connections. Cue Lalli having a "MINE!!!" reaction when someone holds them up and wonders why the hell the others sent them high-heeled boots. And this time, Lalli is not above doing a demonstration of what these can let him do. He spends the rest of the expedition defending his boots from Sigrun who wants to try them on.
I'm am totally void of any base motives such as wanting to see Lalli in functional high-heels and doing badass jumping motions.