I'm not human — there's a flicker of an expression on his face that reads I got that part; it's wiped away almost immediately at nephilim, replaced once again with pure, unadulterated disbelief.

Eloquently, articulately, and with great enthusiasm:

"What?" Sorry kid, he's a broken record right now, this is just. A lot. He holds up a hand as though to emphasize an extremely important, profound point — and then kindly informs Jack, "We're in a wagon."

...give it a second, he's working up to a full-blown rant, that's just the starting line.

"We're in a wagon in a magical fantasy land desert, and somehow... that is the least insane thing about everything I'm hearing right now. I'm- you're- I-" Emphatic hand gesture. This.

Okay, reel it in, Winchester.

There's a little bit of visible grappling with his composure, a deep inhale, a silent goosfraba with his eyes closed. He opens them, and tries again, more slowly.

"You're- a four-year-old nephilim. Hunter. Toddler. That I'm-" he points to himself. Can't bring himself to say the word raising. In conclusion: "This is a wagon."

What he means is: this is entirely too much information to have come to light in the back of a fucking wagon.