You will encounter a variety of characters on your adventure in Animal Crossing: New Horizons. You can invite several of them to join your island, save them from shipwrecks or visit them on their own. One particular person you can show around your island is Celeste, sister of Blathers, a returning character in the series.
To meet Celeste, you must wait for her to appear and progress through the game as you usually would. You have to wait until night comes to your game, and you can find her randomly wandering around your location. Run up to her and she'll briefly explain who she is, her relationship to Blathers, and that the evening will have a meteor shower, which means you're lucky for a shooting star to occur.
Now, talking to her, Celeste explains how you can wish on one of the shooting stars in the sky, and she offers you a DIY project for the magic wand. You can craft the Magic Wand by collecting three Star Fragments and a Large Star Fragment. Beyond that, Celeste is a random encounter you come across during the night. You need to look for her as you wander around your island, so keep your eyes peeled.
The magic wand she gives you allows you to change into different clothes that you have already pre-selected at home. It's extremely easy to change outfits for different times of day as you explore, rather than running all the way back.
