He just gives Tony a look. It's a look like, bro are you serious this cannot be worse than the aliens, or the ambush of wolf tiger things. It's just one little cat. So he slowly opens the door, and has no idea what he's going to find.

At first, he stands back, waits for it to be comfortable with him in its territory. Seriously, Tony doesn't want to sleep so he invites a tiger to be in his room? Wow. There needs to be a word for how determinedly stubborn Tony wants to be when he wants to sabotage his own health.

After a little bit, he starts walking slower, and he's calm about it. He just hopes the damn thing isn't hungry.