Like I speak English and Portuguese, learning Dutch, and (not doing it for the sake of a primarily English-speaking community) but I will often switch between the two, like saying “Bom dia/Oi” to someone or “Tchau!”
I may also falar assim and I don’t do it to show off, it’s just comfortable pra mim. I will mix in a few português words. (Not exactly like this but YKWIM, maybe).
I’m bilingual English and Mandarin and I mostly do this in Chinese restaurants. The real hole in the wall places with the best Chinese food where the servers greet you in Mandarin by default if you look Chinese. Mandarin is more “computationally” expensive for my brain because I’m so used to speaking English so as soon as I have to express something complex I’ll just blurt it out in English instead of stuttering it out in Mandarin, which prompts an English response from the server, and we’ll go back and fourth switching between the two languages.