My buddy Chris sent me this link to a Tom Waits/Cookie Monster mashup, knowing I love both Waits and Monster. What he didn't know is that the YouTube page would have a link to my all-time favorite music video: Hurt by Johnny Cash.
Serendipity. A wonderful creative spark.
Hurt is a Nine Inch Nails song. Or, it was, until Johnny Cash sang it. There are a few quotes re: the reaction from Trent Reznor of NIN, but they basically go like this -- "It was like seeing my girlfriend with another man and realizing she's not mine anymore."
Is it OK to tap into someone else's creativity? Absolutely. Just be honest about it. And own it. That way, no one gets Hurt.