This is what I remember, but it may not be accurate for some reason.

I was testing a level tonight, and when I was finished I had a blocker left with seven seconds left on the clock.  At five seconds I initiated nuking.  When the lemming blew up though the clock was at zero, and then it went to one minute five seconds!  I have tried to recreate this glitch, but I haven't had any success yet.  Just so Im sure I remembered correctly, if anyone has done this too tell me.  If not, tell me any time glitches you know   :-/

Never seen it myself.  Was it in DOSBox or not?

Oh yeah, also, since you use the actual game (Lemmings/ONML, as opposed to CustLemm) to play your levels, which game was it?

It was not in DOSBox and it was being run under the original lemmings.

I've set the nuke 5 seconds before times up on both Original Lemmings and Custlemm. Usually when all Lemmings have entered the house and there are blockers left or lemmings in an impasse I usually set the nuke so I can end the level.

I found another weird glitch.  It involves climbers being able to go through ceilings.  I've seen climbers, tonight, climb through ceilings from one to three pixels thick.  It was weird.  If you shifted the starting point of the climb enough then the climber would not go anymore.  I had one part of a level I wanted to have lemmings go through a one pixel ceiling and it worked.  But then I changed it, and during testing found that it no longer worked.  So I tried a whole bunch of things, and eventually just resorted to shifting the floor down one pixel at a time.  I tested it about three times and it worked  O_O.  Apparently the ceiling isn't always being checked, but the end of the wall is, so they still stop climbing on the pixel they're supposed to.  I don't know if that's right but I'm sure explore can verify it ^_^.

If this is becoming the topic for talking about glitches in general, I have an interesting one:

On Cheapo, the right-click to select a lemming for future skill assignation can affect safe falling distance. I've seen the selected lemming die from a drop that was safe for everyone else. (And since the level required 100%, I was most annoyed.........)

Sure.  I had seen this a few times already in my own experience, especially on walls that are short (like 7-9 pixels tall).  I think I can even give you a fairly exact condition for climbing thru vs. not.  Check your PM in a few minutes.

I think the climbing-through-ceilings trick only works if the pixel diagonally up and to the direction the climber was walking is free. I was just playing Timbalisto's 4th pack, and level 5 uses this trick. I think it only works because of the gap under the twig the lemming climbs onto.

I don't think that's it, because one of the terrains in question was like this and the climber still went through all the stuff in the way.:

  !      
xxxxxxxxxxxx
xxxxxxxxxxxx
xxxxxxxxxxxx
  xxx
  xxx
  xxx
 #xxx
xxxxxx


(Each x is a pixel of ground)

The climber started climbing at the "#" and ended up at the "!"

EDIT:  The exact height of the wall is unknown, but the thickness of it and the terrain above the ceiling are known.

That's very weird...I also noticed that when the pixel of a builder brick covers a gap,a lemming climbing up the wall doesn't climb trough the builder pixel.

It's a glitch in the game mechanics that only works under certain conditions because the program either isn't checking for celing or sometimes when it does it checks the wrong pixel.  If you want the details ask ccexplore for them.

Incidentally, Tim, it would be great if you can e-mail me some samples of your various versions of the wall (and surrounding terrain).  That way I can do more tests to ensure that I have the correct information regarding the climber.

This one is pretty well known and if I recall correctly, works on the DOS version but I don't know about the others.

In the DOS version, if you pause the game as soon as the level shows up, and wait until it finishes the "Let's Go" sound effect before unpausing, the entrance will more or less open up soon after unpausing.  But since the clock is stopped while pausing, in effect you got the entrance to open up earlier relative to the clock than you would if you never pause the game, since the entrance always waits until the "Let's Go" sound effect is over before it would open.

This can potentially allow you an extra second or two of playtime to complete a level.  This is generally not much but it might come in handy every now and then.

Maybe eventually.  The problem is the spot with the three ceiling thing I fixed.  I should be able to replicate it without much of a problem though.