Well when I first saw this episode, I had only been watching One Tree Hill for about a week (I'm still very new to the show) and I saw it was on TV and I decided to watch it. I had no context and had only seen a few episodes in season 1. Boy, was I confused. I was trying to explain it to my mom who hadn't seen any of it before and I kept saying "No, Nathan is the mean one! Why is Lucas being mean? Why are Nathan and Haley friends? What?" Haha. But I really didn't like this episode. I think it was really dumb that basically they just completely switched the roles. I highly doubt Deb would have opened a cafe just as Karen did. Or that Naley would be best friends. I love them completely but it's just unlikely. And why did Lucas and Peyton hate eachother? I know Lucas was supposed to be a jerk, but if it was supposed to show who was really meant to be then wouldn't they actually like eachother? It wouldn't be the same exact relationship Neyton had. I think the writers should have put more creativity into it. Waste of an episode, IMO.
It wasn't to show who was meant to be, it was NATHAN'S dream in hos POV, so it was just him wondering what it'd be like if his dad had chosen Karen and what would have happened if Haley was his best friend not Lucas, and in his dream Haley couldn't sing. It really only focused on Nathan and Haley, because that's what Nathan was thinking about at the time, and it was his dream.