Hmm, I just notice a backroute for the LemEdit remake of Rhapsody in Blue. It doesn't work in Cheapo because the glitch is CustLemm/Lemmings only:
[highlight]From entrance, dig some ways, then bash to the right until you're past the traps. Turn the bashing in the midst of one of his bash strokes to a builder. By interrupting his bash stroke at the right time, it's possible to leave only a small "dent" into the end of the bash tunnel, such that the narrowest part of the dent is one pixel in height. Let some other lemming build facing right while inside the one-pixel part of the dent, he will then get trapped inside the wall. Make him a climber. Due to the CustLemm/Lemmings glitch, he will be able to climb up thru the terrain. Let that lemming walk towards the exit, then have him mine into the steel block near the exit to turn him around. Now have him use miners and/or bashers to complete a path to the exit.[/highlight]
The saving grace is that one of the moves involved needs to be timed fairly precisely so it's not exactly trivial. And if we include people not in this forum as the target audience for our Lemmings remake set, perhaps not too many people would know of the glitch used involving the climber. Still, many of you here know of it.
Please contribute ideas on how best to eliminate this backroute.