Staton uncovers some really interesting Amiga-related nuggets along the way, too:
Lemmings was made on Amiga 500s with no hard drives or internet connection, with all the files saved on floppies. This is one of the reasons that the making of Lemmings has gaps of material and versions lost to time.
Stanton also spends a bit of time in the evolution of the DMA team, and the underlying psychological hooks that make it so irresistibly appealing.[For] Lemmings DMA created an integrated tool for designing the levels, based on the interface of the Amiga’s Deluxe Paint program, which allowed anything built or changed to be tested immediately. This made the construction of Lemmings’ levels a much faster, more iterative process.
Here's one example of Fewell's art, just to give you a taste: