"Prisencolinensinainciusol" is a 1973 song by Italian singer and comedian Adriano Celetano. As the long title and Celetano's career as a comedy singer might hint, there is something going on with this song. You might enjoying watching the music video before I explain the joke.
This song is sung in nonsense English. The syllables, as well as the rhythm they are sung in, sound like English words, but they are total nonsense, with the exception of the refrain "alright". The song was written as both nostalgia and parody: when rock music started appearing in Italy in the early 1960s, the youth latched on to it, with no idea of what the words they sang along to meant. In this song, Adriano tries to recapture how that music sounded to a young rock n' roll fan.
And he does it, perfectly. Even though I know the song is not English, when I hear it, my brain wants to parse the words into English expressions, and every English speaker I have played it for assumes that it is English, and hears words that aren't there. As an English as a Second Language teacher, I like playing this song for my students, and seeing what their reaction is. (One time, I played it for a class, explained the joke, and then waited for the next class, when an absent student returned, and I played it with all the students in on the joke discussing its profound meaning).
To me, the joke has a serious point. Language is usually taught in terms of vocabulary and grammar, but there is a third aspect to language: rhythm or cadence. "Prisencolinensinainciusol" is a song that is immediately recognizable as "in English", even though it contains no English grammar or vocabulary. Even when we accept that the song is meaningless, it is still meaningless "in English". The song demonstrates how much rhythm and cadence, the texture of speech, make up a language.