Technically this is a lore titbit that was revealed in the Jukebox update, but I wanted to make sure if this info was replicated in Splatune 3 (The game's OST) and wasn't like a mistake in the game. But now a specific track's artist has been confirmed in both the game and OST I can bring it to everyone's attention.
If you didn't know, the music that plays in the Alterna levels of the Return of the Mammalians campaign is diegetic and composed by 'Octoplush'. This does include Bing Bong fyi.
Much like their predecessors for Splatoon 1/2's campaign: Turquoise October, the nature of this artist isn't known. They could be one person or a band or a collective, the only clue present is their cover art which shows a collage of Fuzzy Octarians, which implies both multiple members and said members being Fuzzy Octarians. However thanks to Splatune 3 we may have a clue as to one member of this band, as well as their current fate.
In Splatoon 2's DLC: Octo Expansion, introduced us to a new Artist who was responsible for the games diegetic music during it's levels: Dedf1sh. This was an Octoling who at some point let herself be Sanitized by the DLC's antagonist in order to solely focus on her music. Important for this post is that illustrated depictions of her show she still has some of her original ink colour on her fingertips unlike other Sanitized Octolings we see in the DLC (this will be important in a sec). What's important to note is that her music is titled in a spesfic format: Usually a '#' proceeded by a number and a single world. It's a common theory that when these tracks are put in chronological order, they tell Dedf1sh's story from her perspective.
SO! Back to Octoplush! The theming of the titles of their tracks arn't too different to Turquoise October, that is except for one track which can see in the image above: #35 caught. This one track is an outlier in Octoplushes discography and sounds exactly like something which would be right at home in the Octo Expansion campaign, yet is still credited to Octoplush. This implies that not only is Dedf1sh either a member of or a producer for Octoplush (There is precedence for this, as DJ Octavio is the producer for Turquoise October) but also what happened to her after the events of Octo Expansion.
"Caught" doesn't tell us much, but there are a few possibilities. Maybe Dedf1sh was conscripted into the Fuzzy Octarian army and now has to produce for this musical group? Tho for me more likely is 'caught' refers to being caught by the Fuzzy Goo and now Dedf1sh is a Fuzzy Octoling herself.
There's a few reasons why I think the latter is more likely, first off the idea that she would change her very genetic make up in the pursuit of her craft lines up with what we know about her character so far. Secondly it occurs to me that as we've state above, even as a Sanatized Octarian the colour on the tips of her fingers implies she may still have life in her and some kind of free will, unlike the Sanatized Octarians we fight in 2's DLC which both don't have these tips and have no signs of life. So is it a possibility she let herself get caught by the Fuzzy Goo in order to rid herself of the Sanatization? Since she may still have some free will/life?
Thirdly this act of Fuzzying yourself might be foreshadowing a future game play feature for Splatoon 3's DLC. A lot of talk in the fandom has been around if Splatoon 3 will introduce a third playable race. A lot of people, myself included, really are hoping for a Salmonling type playable character and that's IF they introduce one (for my money they likely won't). But IF they DID... Well there's actually more foreshadowing for the case of a Mammaling to fit that role.
Think about the first thing you see in Splatoon 3, no no not the title screen or anything in the game, I meant the Switch Icon when you boot it up. It's of this key art depicting the default designs for this game. While most promo art, the loading screen goo, Amiibo, the box art ect. depicts the yellow Inkling and the blue Octoling, there's also that third guy there, a redish pink Inkling. This is likley to represent a third colour for Tricolour or just for "3" in general. With that in mind look at the cover art for Splatune 3. I expect this redish pink colour to make up the third ink on this cover art but look what we have instead!
I understand these two things are incredibly weak reasoning for "They are deffo gonna do it for the DLC" lol but, it's way more hinting then a potential Salmonlings has rn. I bring this up just to present a possible motivation for the devs to go through all this trouble for this absolutely minor piece of world building, adding credence to the idea of Fuzzying possibly being Dedf1sh's fate, espec if they are gonna feature her as the diegetic artist for Splatoon 3's DLC.
None of this is in anyway confirmed ofc lol but I think it's interesting.