I'm currently on day 5 of playing Animal Crossing: New Horizons. I want my villagers to look cool, so can I give them clothes?
After you've made friends with your villagers (by which I mean after you've talked to them a bunch over several days) you'll gain the ability to say "This is for you!" and give them a gift a day. These gifts can be clothes, and if the villager can wear them (they can wear most shirts, dresses, coats, full outfits, and some hats and accessories, but not pants, socks or shoes) the villager usually will pop on the gifted ensemble. After that, they usually insert the shirt into their rotation of clothes.
"But WAIT!" you say, "That's just not cool enough! I want my villagers to be wearing Insane Clown Posse logos and outfits cribbed from Soul Eater!" Well, good news! After lovable hedgehog clothes-seller Mabel shows up in town three times and you buy a few thousand bells' worth of fashion items from her, she'll establish the Able Sisters tailor shop, and you can pop designs you've made on the back wall of the store. From then on, occasionally you'll see villagers waltzing around your island in your personally-made designs--some of my villagers are wearing my real-life work uniform as we speak.