A mondegreen is when a phrase or word is honestly misheard and the brain fills in the next closest, possible thing. I think it's pretty unlikely that "going on before" was misheard as "left behind the door." Maybe that's how your dad heard it, but it isn't a mondegreen.

The classic: "Lady Mondegreen" for "Laid him on the Green." See?

This thread will go where it will, but then the thread title should be changed to "Religious Parodies V. Umptyzillion," and moved up top to the music section.

Happy Lent,

~Susan