l've been rewatching your Nicktoons Unite video, and remembering your configuration on what a new Nicktoons Unite team would be, I went one step further and decided to make it a whole universe game. Call it like "Heroes Unite" or something. And using SpongeBob's connection to the Big Time Rush universe, I came up with 4 characters who can be in this hypothetical Heroes Unite.
Remembering the rules, they have to save the world and feel like they're capable of doing it, there has to be a Scientist, some type of hero, a person who knows Magic, and a fish out of water (metaphorically). So I came up with this:
1. Julie Dawson (Bonus Stage): So, Julie is easily the first one on mine, because they're a scientist. They built the universe they and Phil live in, they built an entire sitcom reactor that can de-age characters, THEY BUILT A SPACE SHIP THAT ALL THE CHARACTERS WENT IN FOR THE FIFTH SEASON. So, they could easily make portals, breathing capabilities for underwater, etc.
2. DJ Lance Rock (Yo Gabba Gabba): A thing that was surprising in your FRED/ Sam and Cat videos that you didn't mention was the connection between SpongeBob SquarePants and Yo Gabba Gabba. And understanding Lance's abilities to turn five toys into living creatures, and turning them back into toys, he would perfectly fit well for the magic option. The only problem, he is not really probably into this hero stuff, he just wants to have fun. So, I'll probably slip in the MC Bat Commander from The Aquabats in there if he doesn't work.
3: Hero (RPG World): I've never read RPG World in my entire life, but I know his cameo in OK K.O. Let's Be Heroes, so I know kind of the basic gist of the series. So, Hero is a hero (of course) That goes on the quest to save the world. And understanding what his quest is, he would be perfect for this hypothetical game. The main bad guy could be anybody that could destroy the world in the BTR universe, so I could just have Hero adjust his quest to fighting said bad guy.
4. Strong Bad (Homestar Runner): Now, he would be the perfect fish out of water. I know Homestar would be the better choice, but Strong Bad is more notable Strong Bad is a wrestling villain that wrote email responses most of the time. But understanding his more heroic types of fighting, like the time he destroyed his two previous computers, he would be perfect for the game.
5 (BONUS). Who could forget, That guy on Instagram (Nass): He would be perfect for cutscenes, I agree with your list just because of that guy. He could sarcastically angrily just admit the flaws of the bad guys, and talk about how they shouldn't have kissed on the sunset. He would be funny for the game.
I'd probably either make one of the bad guys from The Aquabats The antagonist for the game, or I make like Plankton the antagonist for the game, which one sounds more appealing to you.
Actually, scratch that, Evil Syndicate of Evil (who is probably Elly), CobraMan, Galgarion, and Plankton. That'd be a perfect Evil Syndicate.
Hope this lineup would be good for an expanded Nicktoons Unite-esque game, Quinton.