I LOVE! This!
For the languages it’s not so much “haha I forgot to switch back” because from what I’ve read that doesn’t really happen, it’s like you’ve said– they’re thinking in a language, or something makes sense in one language more than another….or the forget a word in English and Kevin’s like “the…la bibliothèque. La bibliothèque!!! The place!!! 図書館!! La bibliothèque!
And accents are a weird thing bc they stick around YEAH LIKE THAT at least in my experience??? I always get accent hangover.
Also consider: Aaron and Andrew learned German from an American high school + Nicky’s conversations so they’ve probably got some…unique ways of pronouncing and phrasing things. Erik has to bite his tongue to keep from laughing at them, they’re trying to be so angry and intimidating but their accents are adorable
addition bc i grew up in a bilingual household and i am also bilingual:
andrew’s squad constantly walks into practice and says hello in a different language. sometimes neil and kevin forget that not everyone can understand french so they’ll turn to andrew while they’re arguing and he’s just like ??? neil wakes up and thinks in a different language on his run and then greets matt in it, who drops his coffee every time neil reveals ANOTHER language he speaks.
when neil and andrew start learning russian, they speak it around others just to fuck with them, but eventually they just use it interspersed with english and their teams are just. very confused.
BONUS: one time both neil AND kevin forget how to say a word in english so they text jean who doesn’t respond, and then halfway through practice kevin shouts out “GRAPEFRUIT!”, which makes neil scream/groan in sudden realization, and the freshman scream because they’re suddenly worried that perhaps KEVIN DAY has become unhinged. nicky tries to learn french, but all the articles are screwing with him, and after saying “im horny to see the prostitute” (je suis excité pour voir fille) he gives up.