It's Splatoon! The colorful shooter series from Nintendo about squid (and octopus) kids. Since the release of the first game in 2015, it's become massively popular, with two more sequels, live concerts, a manga series, and a shit ton of merchandise.
I was first introduced to the series with the first game's E3 trailer in 2014. At the time, a friend and I were obsessing over squids and had them as a sort of inside joke, (for reasons I cannot remember) so naturally it immediately caught my eye. I passively kept an eye on it up until the game's release, and shortly after my parents surprised me with the game and a Wii U after graduating middle school. I was immediately hooked, and played the game obsessively throughout that whole summer and for a long time after. My interest was more passive for a while after that, until 2018 when I finally got a Switch and was able to get back into it with Splatoon 2. Since then it's been a pretty constant interest for me, with long periods of playing on and off. I've made quite a few friends through the series, and it's still one of my favorite things to do with them.
I love both sea life and speculative biology, so naturally the Splatoon universe is one I really like thinking and talking about. While there's a lot of canon lore to go into, there's also plenty of room for speculation and fan creations, so even when you run out of canon content things are still interesting. Splatoon is a really special series, and I'll love it forever <3