I showed this video to my husband. Afterwards, I was surprised that seemed less impressed than I had. Then I realized, I'd said "schaud das mal an!" and not "check this out". His brain was in German mode and he was unable to connect the pictures to the words, because he wasn't watching in English. I found this incredible.
I've had the experience of language disorientation. On several occasions when conversing in one language, a person has interrupted me in English, my native tongue. It is not unusual for me to hear it as gibberish, and to have to replay what was said before I could understand it. The delay can be confusing to the people around me.
I had a similar experience when studying for my German language exam in graduate school. I was translating a scientific paper from German to English and came across the word "Ar" at the end of a sentence. I studied my German-English dictionary and the Ar I found there did not make any sense. After stewing over it for a good length of time, I realized that the Ar was not German but Chemistry; Argon made perfect sense in the sentence.
Emmett
I love it!
One of my more frequent experiences with language disorientation is when I overhear conversation. "Where the Swiss? German? British?" someone might ask when I'm recounting eavesdropping. I have no idea when I think back.
I'm fairly adept in Spanish and somewhat conversational in French, but I'm fluent in neither. One of my aunts went back to university after her five children left the nest and got a degree in Spanish (she already had a degree in History, but she didn't do anything with it since raising five children is surely a more-than-full-time job). Anyway, she said there was some revelatory point during her studies abroad in Peru at which she realized that she was no longer translating Spanish to English in her mind, but rather just understanding Spanish as its own language; and that was what she called fluency. That fluency seems so far away to me — I also carry baggage from my pedantic worry that I might say the wrong thing in English, and, therefore, I speak less in other languages than I might. To you fluent speakers of multiple languages, is there truly an epiphany that let's you know you're actually fluent?
(I ask this because I never experience the "disorientation" you speak of, and think that's because I hear other languages I'm familiar with as "other" languages, and so prepare myself for internal translation.)