Re: What happens when you leave a crab unchecked...
Any actor in confined spaces will do this.
At one point, in B24, I was playing with two friends, and I put my brainbot in a small square of emptiness near the bottom of the map, for protection.
Unfortunately, I lost that particular round when my brainbot managed to foot-tunnel a very narrow hole from the bottom-left corner of his cubicle to the bottom of the map!
Moral: Use brain-cases, they're a little less adventurous!