The very beginning of my serial features a superhero being murdered. She's the indestructible, overpowered Superman type and really popular. And she gets her throat slit open.
I recently watched the first few episodes of the second season of the TV show Powers and realised that the beginning of my serial is from Who Killed Retro Girl, which I read years ago and then forgot all about (except in my subconscious, apparently).
It's not a huge problem, because everything after the murder is completely different. I just thought it was really interesting how something I read years ago, and then forgot all about, was such a big inspiration to me.