It also works in German and I'm relatively certain it's not translated outside the model itself. I've asked it to generate puns incorporating certain words and while the English results were subjectively somewhat better, the German ones were still "fine" and definitely wouldn't work in English.
ChatGPT is so crazy it even works in fluent Thai. That's better than any machine translation I've ever tried so far. It even takes cultural differences into account. For example when you ask it to translate "I love you" into Thai, it mentions, that normally you would not say this in the same circumstances as you would say it to your lover in the West, correctly explaining in what circumstances people would really use it, and what to use instead. That's revolutionary for minority languages without a lot of learning material available online.
Also I am a native Swiss German speaker. For those who don't know: Swiss German is a dialect continuum, very very different from standard German to an extend, that most untrained German speakers don't understand us. There is no orthography (writing rules), no grammar rules etc. It's a mostly undocumented/unofficial writing system. Only spoken, and the varieties are vast. And guess what, I can write in completely random, informal Swiss German dialect and ChatGPT understands everything, but answers in standard German.