By far the most interesting and significant part.The key point is that there was no programming or learning involved to create the behaviors. The connectome of the worm was mapped and implemented as a software system and the behaviors emerge.
Also by far the most amazing achievement in terms of sheer work by Sydney Brenner's group way back in the day. They SERIAL SECTIONED a few worms and imaged with electron microscopy to build a detailed anatomical map of every cell, with special attention to neuronal connections. This is an insane amount of incredibly tedious work. You can see the fruits of their labors at the Worm Atlas.
I had never looked at the protocol for that experiment before. Jesus christ. "how many grad students does it take to scan a nematode?" etc.most of the reconstructions were done by hand from a total of about 8000 prints.