Okay, he may not have ever had a pet, but part of being in an intergalactic community means you get good at guessing the nonverbal stuff, and there's clearly something else Crookshanks wants to say. So to speak. Jim frowns, unsure of why the cat is hesitating. Isn't this an emergency?

"Do you need backup?" Is that even possible, he wonders. If Hermione had to shut the door somehow... but crazy as it sounds, Crookshanks has pretty good judgement, all things considered. Maybe he knows something that Jim doesn't.