He's ... a human wearing a rat costume? He's got a shirt on under his fur crop-top (is that rat fur?!), and the tail seems to be attached to that, and I think he's got close-fitting shoes (same color/stuff as the tail?) on rather than having bare feet, as his ankles are a different shade. Was he hiding behind the rock the clank tapped, or under it? It seems to be in a different orientation in the fifth panel than in the fourth.