Knock knock, sir, there's a nervous entity at your door as a tentacle boi because he's been weirdly anxious about human-ness ever since being introduced to the question of why he looks like he looks.

He is also weirdly anxious about coming to Arthur's apartment. An anxiety he doesn't have going to see Sally or, he notes with confusion, Crichton. But with Arthur, even more with John present, Yellow is the invader now. Uninvited. Not one of the people meant to occupy the space. He knocks with a tentacle from the opposite side of the hall.