In Ooblets, the Ooblet creatures are the primary companions for you and the residents of Badgetown. You will find several of them wandering around your town that you can interact with and potentially dance against to gain their seeds if you beat them. You can take that seed back to your farm to plant and turn into that Ooblet, and it follows you around town to dance against the other Ooblets. New Ooblets won’t show up each new day, and the best way to unlock new ones is to level up and gain access to wishies.
You need wishies to unlock access to new Ooblets. You can find the options available to you on the wishies rewards screen by looking and picking them from your Grumboire or the wishing fountain at the center of town. The first Ooblets are available to you for 50 wishies. After you unlock those, you need to wait for the next day to see them around town.
All players gain access to more Ooblets to unlock by leveling up. You need to consistently be obtaining wishies, which you can do by completing any of the three daily tasks or by earning any of the badges. You can view the Oooblet glossary in your Grumboire to see how many Ooblets you have encountered, how many you have, and how many you still need to meet.