Slugs may not look like the most entertaining creatures, but that's only because you've never watched one for an extended period of time.
When you observe a slug, you have to make sure it can't see or hear you, otherwise it will stop being interesting.
Well, maybe slugs aren't as interesting as they are self-interested. If this slug had moved a little faster, I could have provided you with more varied drawings. Alas, this was as much of a learning experience for me as it was for you.