Fairly mundane maybe, but I thought this was interesting now that I've considered the 'cause' of it.
This morning we slept in late and during that time I had a dream about something and nothing, but the important bit was I could hear a man talking Swedish, but every so often he'd use an English word (e.g. 'you', 'take', 'need', 'today', 'each', that sort of thing.)
Random words which he should have used the Swedish equivalent of, but which he was saying in English, i.e. I understood them. The rest of the words in the sentences were ones I couldn't understand. So he was speaking in properly constructed sentences, but switching between the two languages.
But the thing was... whilst we were sleeping in late, of course the radio was playing as it comes on with the alarm. And it was on, as it always is, Sveriges Radio P1.
So I think my brain was subconsciously hearing the radio, and instantly translating and replacing the words that I can recognise, into English.
(As opposed to when I listen to it while awake, in which I clearly hear the Swedish word and mentally translate it which sometimes takes a second or two).
What fascinates me is the instant replacement of the words; in the dream I know I didn't hear, for example, "behöver" followed by "need", or "varje" followed by "each", I only heard the English equivalents.
The brain is fascinating, isn't it.