Danny, Sam and Tucker developing their own language, it mostly being a blend of Ghost and Esperanto and gibberish. They use it to communicate to each other without anyone else knowing what they’re saying, when they need to speak about private things, communicate battle tactics without the enemy knowing what they mean, or just to annoy people.
and then they take it a step further and start speaking in codes in the trio tongue. brief shorthand to get info across quick, like “d7 to mark2-0-K down 9 at count.” the trio are gamers so it’d be similar to how they plan plays, only quicker.
and everyone thinks they’re crazy for having this made up language. Dash teases them because “Didn’t you know you were supposed to grow out of kiddy playing, you dweebs are regressing. Wonder how long till the diapers come into play again.” and they just. talk about how dumb Dash is. right in front of him. because Dash can’t understand. and they laugh about it. and it pisses Dash off. It gets to the point where the trio speak nothing but their own tongue when they’re not in class. they develop a written form of it using ghost letters but they change which letters are assigned to which sounds and combine some letters to form new ones so if even a ghost tried to read what they write it would just be absolute nonsense on top of a language that it wouldn’t know.
Jazz tries to get Danny to teach her, but he refuses because he doesn’t want to confuse her. Teach Sam and Tucker how to speak the handful of ghost sounds that humans couldn’t really replicate had been hard enough. Valerie is confused by the new behavior, but quickly becomes suspicious
when she overhears and recognizes a few words being spoken by Phantom.
Jack and Maddie steadily get more and more worried about this kind of behavior because they even speak it to each other when they’re all together in their house. Sam’s parents Blame the Fenton’s for corrupting their daughter by teaching her devil tongues and they don’t believe Jack when he tells them that the language wasn’t Ghostspeak. Tucker’s parents try to not mind but it starts to worry them too. all three sets of parents try to ban the Angela by way of grounding or the threat of not allowing them to see each other anymore, but that just causes the three to shut up. and not say anything, secret language or otherwise. so they eventually just agree to let the kids continue to speak the language though they’re not happy about it, but for their part the trio do cut it down a considerable amount.
Danny accidentally writes part of his papers in the language. Mr. Lancer is beyond done.
And Vlad just doesn’t even try to understand. Danny tries to annoy him with it but Vlad just ignores him. When Danny doesn’t stop, Vlad begins speaking back to him in an equally nonsensical, fake language, one that he, Jack and Maddie made back in college. it becomes a virtual nonsense conversation because they keep talking to each other but they have i no idea what the other actually means. sometimes it evolves into arguments other times its surprisingly calm and they seem to communicate well. Danny uses every chance he gets to insult Vlad. Vlad uses the opportunity to reveal, in detail, his exact future plans right to Danny’s face.
In regards to that language headcanon that everyone’s getting excited about…
Jack Fenton is not an idiot. He loves to blabber on about a lot of things, and he’s a bit clueless at times, but there are small clues throughout the series that he IS an intelligent man. Why would he build a Ghost Gabber if ghosts communicated in English? Remember, the series addresses a lot of modern beliefs about ghosts. Why would they forget EVPs, one of the most popular tools for ghost hunters?
Ghosts often don’t speak in sound that can be understood. Thus, the Ghost Gabber most likely records EVP and relays it instantly.
It translates Danny’s speech. Presumably, he has the ability to speak ghost, and just doesn’t realise when he does so.