Here is version 1.0 of Jack and Jack. It is not finished yet as there are possible stucks and deaths that can lead to loosing one of the twins - but sometimes it is possible to bring him back to life!
Edit: I've replaced version 1.0 with 2.0! Added 3 rooms to demonstrate what happens if one of the twins climbs between rooms, and, well, you'll find out....
Version 2.0 upgraded to 2.1. Added a sign to help players to avoid cheap deaths.
Added: This mansion is evolving fast. Version 3.0 is now ready for download. Added 3 more rooms to make one more demonstration involving ladders and made a minor change in the starting room to avoid cheap deaths when going to the exit room.
I experienced that many deaths for (at least) one of the twins, when going from one room to the next, that I never could get that last blue keys in the leftmost room.
Usually I ended up with the remaining Jack stuck in a gap (he could get out via that secret passage, but he couldn't get to the leftmost room anymore....
Am I too dumb, or is that the problem you mentioned (when you wrote 'not finalized....')?
Have you tried jumping between rooms? Note that the second twin must be at certain positions to land on the correct places in the room to the left of the starting room.
After much thought and consulting with Aquamat (thanks for the testing) I have decided that IT will NOT go to the complete mansions list. It is too erratic and if I change it to avoid some weird behaviour some of the two-Jacks-effects are ruined. So, IT is just what it is, a demonstration of what is possible with 2 Jacks going between rooms. It is very easy to play once you know how to avoid deaths which can lead to disaster. I can provide hints or even a walkthrough via e-mail if requested.
For some reason, when Rose sent me a movie of her beating the end of Volcanis, my computer didn't know what kind of document it was and MM wouldn't let me open it up! :'( :-? I tried making the default opening up thing to MM, changed the icon, and everything. Nothing worked! :'( :'(
Why doesn't it work?? All you gotta do is go into prefs, make sure recording is on, once you beat the mansion, send the movie in a zip file here! If you can't find the movie, search for your user folder of MM. It in, Libary/App. Suport/Midnight Mansion/Usermovies/(your user)/there it is!
Here's a movie of me beating Echo keep! Boy I love that mansion! Don't laugh at my silly mistakes. Didn't suspend or open save the whole way through. (I think)
I like it how you get the blue key in the room to the left of the starting room! 
Beat it in 30 secs!
