Castiel hadn't known he was supposed to be getting help with the Winchesters. He hadn't known any angel would want to be by his side helping the Winchesters, but seeing you show up and claim to be Sam's guardian...

"So why show up now?" Cas asked, glaring at you as you sat down. How dare you show up and start trying to help them more than he can. "You're going to lead them down the wrong path if you keep eagerly answering without so much as a moment of thought!"

He's getting sick of watching you dancing around the boy's heels and yap like a small dog. He's been here longer, he knows the boys, "You say things like what you're saying too often and they'll start acting on it and they'll get themselves hurt."