I had this idea i thought what characters it can be:
GNU: Libre blast(temporarily knocks you. out) ,propitery jail(Gone from the game ofc it has a cool down.
Tux: fish throw(throw fish into your enemies),Run. blast (run into your enemies and blast them)
Kiki (krita): Paint blind(blinds your enemies)
Pepper and carrot: witch stuff ig
Game name: Super Libre Bros

What's style are you trying to go for? N64 smash, melee (game cube) Wii, 3ds, switch ultimate?

That is going to matter alot to my recommendations.

N64: add clippy or a knock off version, add bonzai buddy

Melee: add a shitty master cheif clone. Orange faceplate, green armor with a purple fat girl AI ...you know, to avoid copyright

Wii, 3ds, switch: add skibbidi toilet, harambe, sanic meme, and a gen Z broccoli haired kid.

Don't downvote me I'm just spit balling goofy shit. It would be cool to have a character per meme or time frame of memes.

Will the Rust crab be in it?

How do I follow a user on boost app?

Tux should have several skins that represent different distros like a red fedora for RHEL lol.

My other dumb suggestion is having nmap be a floating blue eyball

So broadly you will find categories in games like Smash Bros and so on. Some characters will be heavy, some light, some fast, some slow, some strong, some weak, but each trait creates an axis. The ideal distribution of characters is to have all areas of the multidimensional space filled or if not filled at least alternated.

For example, you should have one heavy, fast, weak character, one heavy, slow, strong, but maybe not a heavy, fast strong or a heavy slow weak. You can chart them on a two dimension axis at a time, then use the characters from Tuxcart etc to fill the space based on what makes sense, eg the Gnu should be heavy but also fast, but it is definitely a prey animal, while penguins are smaller and fast with a more moderate attack level, maybe even weak.

Once you have some of the extremes filled you can consider subversions of the paradigm. For example, a compiled language is slow at creation but fast at use, so maybe a mascot for one of those could have two modes, switching state and therefore characteristics.

Another thing to consider would be the dynamics of your interactions. Are you going for the jumping around of Smash Bros? If so, lots of the details about their camera work can guide your decisions. What about the overall pacing? Do you want frenetic play like Smash Bros? Combos? Strategy? Lots of things to look at there with a narrative approach to the characters as representing their projects, for example Wilbur is smaller and supposed to be super modular, so maybe having quite a few modes with different characteristics would work, while something like puffy is great for water levels alongside tux and any other aquatics.

One of the carriers from Endless Sky as a calldown

Clippy as a hidden character.

The characters could start out as just the ones in supertuxkart and then go from there. I'd be happy to help with the movesets, balancing, and playtesting. I don't have any experience with Godot yet but I have been meaning to learn!

I like the idea of your game! What other characters would there be?

Penguins like to slide into water so maybe Tux has a belly slide move.