Haha, I mentioned this TAS a while ago, in the "least time" challenge thread, but I never actually watched the video until now.
I noticed a few things ("mistakes", if you will) that mean the time can be improved:
- On "Just a minute (part two)", he digs a pit with diggers and bashers to hold the lemmings, and then releases them at the right time. (My own experimentation with this level suggests that this is the best method.) But, on "Just a minute", he uses the free pit instead, and ends up taking 6 seconds (by the in-game timer) longer, when the same solution from part two would work equally well.
- For much of the video, I thought he was totally unaware of the sliding trick (a known timesaver on many levels), or maybe the glitch just doesn't work on the SNES version. But, on "Steel mines of Kessel", he uses it! This means there are huge chunks of time to be saved on some levels.
- On "Time to get up!" he could have turned around and started building to the top much sooner by placing two bridges on top of each other (unless the mechanics forbid this, which I very much doubt) and then building into those.