Lemmings Crossover - take other classic same-console game franchises and use level features/abilities based on that. Or similarly but just on movie based franchises.
SMS designs could borrow from:
Alien 3: Flamethrower ability, hostage lemming cages, predators.
Batman Returns: Grappler ability. Cape ability to sail down across gaps.
Alex Kidd in Miracle World: "Underwater" level with an octopus tentacle moving platform.
Sonic the Hedgehog: a loop from Green Hill Zone, speed shoes ability (could help past traps), a ring that gives a lemming two hits
etc

Some amazing news! This weekend on Saturday at 4pm EDT 10pm BST (EDITED TIME), I will be showcasing SMS Lemmings Fun in SegaCrew's Segalympics marathon!! Ever since I picked the game up it's been a total pipe dream to get it into an event, so this is a really great opportunity and I'd love to see as many of you as possible in there cheering me on. Hopefully we pick up a bunch of new runners to any version! You can watch the action live at https://www.twitch.tv/segacrew

I started the final round of work on Tricky SMS a while ago and have been able to incorporate the walking on water glitch from Squidgy in to a solution already, so thanks to him for that discovery! I made very good progress with a few levels thanks to pixel perfects. I've been able to go super aggressive but also very safe in various methods so far. Perhaps my favourite optimisation among the first 12 levels is for Been There, Seen It, Done It. It perfectly showcases the p-perfect accuracy of these solutions as well as the need to pragmatically pause the game if you need to make such a setup. I would LOVE to be able to do this at a marathon event one day, it would look so good.

https://www.youtube.com/watch?v=SjTxeC1mWls

Meanwhile I have started streaming at www.twitch.tv/petaq_src and many of these streams include some Lemmings Tricky practice, which will soon move on to actively optimising levels 13-30 ahead of WR runs. I will try to make some of these streams US-timezone friendly and I would love to see anyone who is interested in this sort of work pop in and enjoy the inner workings of the game.

I only just realised that this is a real thing in the same way that L++ and Lemmix are, no idea how I didn't twig for so long but I'll take some time to get the hang of it and the vagaries of the tiles, then get to work on a series of levels. Requests welcome since I have plenty of time to make a whole bunch! If anyone ever wants to set challenges for either speedrunning levels or just causing me some chaos, I'd be quite happy to take on allcomers and post the results to my Youtube or even in future stream me playing a pack of SMS levels blind like they do with mario maker. Who knows, a community built pack of 30 might become a category on Speedrun.com one day!

I bumped the SMS Fun WR down to 31:42 even with two resets and some hairy moments. The resets are deceptive: the one in 10 is about a one in twentyfive occurrence and not something you consciously think about during runs. 30 is just a nasty level full stop and if I improve this run I should definitely look at changing the final action to prevent them getting stuck.
5, You Need Bashers is the fastest I've ever done thanks to a pixel perfect web-bash setup and proper nuke timing. Improvement to 11, Keep Your Hair On by bombing the trail bashing lemming rather than one of the advance party to reduce the tail, and check out the perfect in 13, We All Fall Down. I added a defensive bomber position into 14, Origins and Lemmings to enable safe climber assignment; I also found a way to dig/bash from the top of each high pillar and ways to reduce the tail but they're effectively uselessly aggressive in a marathon run. You may also be highly interested in the swagtastic solution to 29, Worra Lorra Lemmings, which relies on both a pixel-perfect bash and a pixel-perfect bomb. Ultimately the time can be put down to very near 30:00 dead, but I'm going to start working on final optimisations of Tricky now which may take a while since everything can now be pixel perfected. I hope to be able to stream in the coming weeks once my tech is sorted out so if I do I will definitely try to showcase our wonderful game to a wider audience.

https://youtu.be/0pnfuAo8sF8

Hi Simon, yeah that's me, I had planned to come back to Lemmings SMS this winter and I found a large number of perfections to my old solutions which I've now nearly finished. The full playlist can be seen at https://www.youtube.com/playlist?list=PLOTsjhPmEfJd9ccq6yzH6VL9ObH9M9hYr and the fastest possible 30-level run is now down at just under 31 1/2 minutes. The improvements generally fall under either pixel-perfect actions (bridges, bashes, even floats), tighter tail management, or better management of lag. The definite highlight of this is

-Don't Do Anything Too Hasty. You think you need blockers to solve this level? Think again. What used to be a high-lag run killer nightmare is now a gimme.

What used to be a run of risky levels from 15-23 is now mostly safe. 9 is just a lag nightmare, the only stress now is 17/18 which demand precision. Will be attempting to lower the WR to around the 32.xx mark soon then perfecting Tricky.

A sort of new glitch for SMS: when mining, if you pause and unpause on the right animation frames (it can be done easily on manual without a turbo), a miner can be coaxed into leaving strips of land undug behind him. This can create a little camp for other lems, who on the short side will slide up and over, but once inside the ground is too low to let them escape.

EDIT: the trick also works with diggers - pausing and unpausing rhythmically on the right frame will leave the topsoil partially broken allowing the digger to pass through but the other lems to remain atop.

If done carefully it can also be used to slow a bridge builder down relative to the group by pausing in a way that prevents hi laying his current brick.

https://www.youtube.com/watch?v=PuYprH5p87Q

I have now almost finished optimising Tricky levels on the SMS. The current fastest projected completion is down at 40 minutes 23 seconds, though a more realistic target is below 45 to account for safety and human error. If you want to watch the playlist of optimised levels go here:

https://www.youtube.com/playlist?list=PLOTsjhPmEfJeElqnBUB6wPCj2k98ds9H8

and if you think you see any flaws in my methodology please let me know!

Hey Nch advised me to share an updated WR video where I commentated the levels. Please excuse the bad mic quality (inexperienced at that) but I hope it helps shed light on the way the game is ran!

https://www.youtube.com/watch?v=5TEqSSNH5XU

I broke my Fun WR down to 35:55 with just one death in a small level!
https://www.youtube.com/watch?v=IrJKRRLdbb4
I think the swaggiest level is 22, Go For It. That transition between the last builder and the lem reaching the bash area is literally frame perfect, and had I set that straggler lemming as a builder a few frames earlier, the execution would have been perfect.

I've started optimising Tricky Levels again now, and I've already shaved off some huge chunks. Take a look at this beauty:
https://www.youtube.com/watch?v=z0wTPTyDhOg

I did a run the other day that failed in level 29 when I was on for a sub 39 minute run I've optimised all the SMS levels and among the standout results is this insane one which shows the importance of lag in avoiding both too many lemmings, and avoiding bombers:

https://youtu.be/qPuDnSn7Bsg

EDITED: Adding in the between-level transitions, the lowest possible completion time is currently 33:21.3, so I can realistically expect to set a time beneath 35 minutes with good execution.

EDITED: Latest WR down to 41:55, which would be sub 38 if I hadn't bloopered two levels
https://youtu.be/coWvgAwNFps

Apologies, I cannot count under pressure and neither me nor NCH picked up the mistake til just now :'D

Oh I'm sorry I meant what I said as a joke about how esoteric my thread is

Lag in the SMS game starts whenever you have 11+ lemmings on screen, and ranges from as benign as 1 frame in 9, up to 2 frames in 7. Explosions seem to be a troublemaker too, and the best thing to do is keep 10 or fewer on screen at any one point, though a friend and I are working on understanding this because the byte that counts sprites on screen acts weirdly when lemmings cross each other. Current theory is that it's to do with horizontal positioning - 20 lemmings on screen who are all walking up and down a long bridge cause far less lag, and it's the same if they're on a very undulating piece of terrain.

Anyways, with that in mind I've started tackling the Fun levels, 17 is very interesting because unlike the other versions you have no floaters to take advantage of. I found a super aggressive solution that looks really awesome though: www.youtube.com/watch?v=AcGpxjp_kKU

Good news everyone! (What are there, 4 of you? )

My buddy Calindro and I created an SMS lag monitor tool which is going to make it super easy for me to dig into the slowdown the game provides. You can see a short clip of its use here https://www.youtube.com/watch?v=BLGrBL1DAGU&feature=youtu.be but I think I've already got a superior display method which is more akin to a seismometer. If anyone is interested I can post the traces of several level playthrough as they stand at some point. If not I'd be happy to stop clogging the forum and just let people come to my playthroughs when they wish

Mm, I'd seen Gronklems' work on a couple of levels though I'm sad for him to hear that the lag is erratic. It seems to be much more uniform on SMS and since I'm doing rta speedrunning, I'm spared the need to do superhuman movements. My latest improvement, on Lost Something?, shows evidence that bunching lemmings into a very small space so that they move almost as one, can significantly help matters. I knocked 90 seconds off Sega Three just by judicious early killing. I started posting RTA optimal solutions on my channel, anyone reading is more than welcome to look at these and suggest improvements or just generally enjoy them