One time, I wrote a short spec piece called "March Of The Penguins". Not terribly complicated at all, and I thought I had come up with the perfect "motif" for the penguins- a sort of plodding yet playful piece of music, like penguins themselves. Basically I was right-I could hear and see the perfect match between visuals of penguins and the music I came up with. I thought to myself "well played sir!"
The next day though, I found myself watching an episode of a certain, dysfunctional, animated family show. As usual, the main titles blasted out in that "old time", break-neck speed, cartoon frenzy- business as usual EXCEPT a tiny alarm went off in my brain about the main titles. I watched the show then fired up my keyboard to investigate the cause of that "alarm".
It turns out that I had changed the theme to "The Simpsons" to suit my own purposes,even though I hadn't been aware of it , at the time. Now,when I say "changed", that doesn't mean I changed the basic tones of it-BUT I did change the rhythmic notation, tempo AND my orchestration of it was certainly going to be different from "The Simpsons".
Instead of discarding this, I decided to keep it! If John Williams can "lift" from Stravinsky (STAR WARS) and Danny Elfman can lift from Christopher Young (HELLRAISER 2 for BATMAN-main title theme) with NO dire consequence whatsoever, then I'm keeping my "March..." :)