There was a lot in Neverland to get used to, and as much as he wanted to get to know her, he needed to tell her some things, break some things to her gently... except he was Mars, and he wasn't exactly known for being delicate.
"So, there's a huge difference in the two of us. I'm a lost, the new kid Jack, he's a lost too. Basically, if you have a planet or a moon name, you're a lost, if Peter gives you an animal name, you're something called an imaginary boy. You are Puppy, that makes you imaginary."