I could see the voice actor learning a sentence or two but on occasion the bit goes on for a couple minutes. I feel like with a cartoon it wouldn’t be that hard to find a stand in who sounds close enough or use whoever does the dubbing for that language.
Probably just the voice actors, most of the time the pronunciation sucks. Like in Oppenheimer where he suddenly talks Dutch, just complete gibberish and all the scientists are there smiling and nodding thinking “What an ass, thinks he can learn a language in a few weeks”.