[if kni doesn't pose as a threat, then there's little reason for a tiny crab to try and attack him. it meanders away, and kni escapes a possible pinch attack unscathed.]

They turn red when they're boiled alive in hot water. There's a protein in their shells that releases in the heat, and that's what turns them red.

[red meaning death, an irony that thankfully goes over kni's head. ignorance is bliss.]