When my first kid was born I often found myself singing that song to her when she cried. I didn't know why my brain jumped to that song so often, and then a couple years ago I re-watched that episode and was like "oh yeah, that's why. The show I watched every day as a child left some things in my subconscious." I also know that I've reached a certain level of stressed/anxious/depressed when I start singing "Que Sera Sera" to myself like Ned Flanders does in "Bart's Comet".