That first paycheck opens up a whole realm of possibilities that you'd only dreamed of before. Before that check, it was always someone else's money - your parents, grandparents, a sibling in exchange for a favor. But that first slip of paper or electric deposit in your bank account...that is your money. It's proof of the work that you did to earn it, and it's yours to do with what you please. Of course, the reason you got that minimum-wage job was the money. But if you're lucky, the job becomes something you enjoy. And if you're not lucky...well, you'll still remember the experience.
You'll remember the people you worked with, if not by name then by characteristics. You'll remember that couple that you didn't know was a couple until after you've left, and wonder how you didn't put it together in the first place. The man bordering on elderly that definitely didn't look like he belonged at a movie theater? You'll remember him too, especially how irritated he made you feel when he was giving you advice about how to do your job. Seriously dude - you're the old man working a minimum-wage job with a bunch of teenagers and people in their early twenties. Oh yes, and you will definitely remember the guy that got hired with you that you already knew had issues. You'll sort of wish you were there to witness it when he got fired and apparently threw a fit in the parking lot, except that you were already really uncomfortable having had to speak privately to your manager about him...or maybe that's just me.
You'll remember how you got the job in the first place. Whether it was an online application that you didn't really expect to hear anything about or a friend who recommended you. The interview that felt like forever but was only ten minutes long, or the interview that took literally a minute for them to say, "You're hired!" and you thought to yourself that they must either be really trusting, or really desperate for workers. (It was probably the latter if the previously mentioned incident was any indication.)
You'll remember cleaning the bathrooms. If you lucked out, you never had to worry about explosive diarrhea that came out of the kid who had too much popcorn. If you lucked out, the bathroom wasn't actually the grossest thing you had to clean up. The grossest thing you had to clean up, in fact, was what was underneath the popcorn machine that had a broken oil valve. No one had cleaned underneath it in almost a month. Unpleasant was such a vast understatement, and you couldn't come up with a better adjective because you were so busy trying not to throw up and add to the mess.
You'll remember that the broken oil valve was just the beginning and that the entire popcorn machine shut down shortly thereafter. The shift you had where you had to tell customers that there was no popcorn? Well, you finally understood the stories on the internet about rude customers. The next day, enormous bags of popcorn were driven in from a town over an hour away, but it wasn't the same as the nice machine popcorn, and you weren't allowed to eat it because of the limited supply. But that's okay - if a pretzel was broken in the package, it couldn't be given to a customer. Instead, you got to eat it for free. ;)
You'll remember a million little things about your first job. The first time you worked the cash register, the first rush of people, the first time you were allowed to do inventory, and a dozen other experiences that built up that time in your life. It's one of the best things to carry with you as you grow.