In Hatchet, what happened when Brian laughed and called himself a "City Boy"?

Brian laughs at this because his transformation as a human being has dramatically changed. As mentioned in the above answer before me, Brian used to be a "city boy" because of his history and experience within the city. He would waste food, and not take full advantage of the resources around him. This is complete opposite thinking that he had in the wilderness. Instead of being given food and taking it for granted, Brian now had to earn everything, in order to survive. This type of experience that he went through, would be very life changing for any human being. Having to be placed in the complete opposite type of atmosphere, such as the one Brian was placed in, forces you to adapt and step outside your comfort zone. For Brian, this was a necessity for his survival, and when he laughed at the "city boy" reference, it put into perspective how much he really had changed.