I spoke with my 29 year old daughter, actually read this thread to her. She's a very intelligent and intuitive woman and works as a stage set designer (so, an artist). She has battled with an anxiety disorder for most of her life, but is not bipolar. We discussed this thread & my daughter said that she definitely relates things people say to song lyrics and to scenes from movies. She said she believes that most people do, but that the difference between those who do the "normal" relating between the spoken word to lyrics or movie scenes have a brief thought of either the lyrics or the movie. Those who have a problem with relating the spoken word to lyrics/movies are the people who cannot get the lyric or movie scene to go away...it becomes obsessively stuck in their mind so it interferes with functioning (sleep, reading, work, whatever). Someone who is full-blown manic might feel pressured to talk about the intrusive lyrics, songs, movies, etc. Someone who is schizophrenic might become agitated with the association and act out that agitation.

Basically, I think (as with so many mental health issues) there is a "range." On one end is the normal association between the spoken word and a song or movie ("normal")...onto an obsessive association (troublesome)...and so on until a point at which someone with severe mental illness associates the spoken word with a song or movie and that association is all-consuming, entirely disruptive.