What does "creative" mean anyway?

So, I spent a good part of the day yesterday poking around the internet for resources to use on my next hobby project. I'm not telling anyone what it is because, well, revealing a big secret is kind of fun for me sometimes and I'd like to keep it to myself for awhile. But what I will say is that while I had a lot of fun looking for materials and I'm excited about the project I feel that it's kind of derivative. It's a project that's based on riffing on something that's already been created. This makes me feel a little apprehensive about the actual creativeness of it all. Can I really claim that I'm being creative and making something when it's based on other people's work?

Some of the people who know me might be aware of this thing I call the “Star Trek Musical”. I started writing it when I was 13 and, based on the fact that it is “copyrighted” to “Angie K****** Enterprises 1996”, I finished it when I was actually 14. This, in combination with the other Star Trek based short stories I used to write around this time, has always been part of my claim that I used to get creative and make something. But is it really being creative? Does creativeness imply that you create something mostly out of your own head and not have it be part of something other people made first? Can I be creative and claim to make things if I only kind of riff on what other people do? I don't feel terribly creative right now in terms of making something new (Creative works and academic papers for my classes aside). It makes me wonder what's wrong with me. No many people enjoy being around uncreative people. And I haven't spent much social time with anyone other than Ted recently so maybe there's something there.

The problem is that I really enjoy doing creative projects based off of stuff other people do like writing a new story involving television characters that I really like or making tongue in cheek handcrafts that riff on a theme that's sure to make people laugh (See “Paint By Number Wil & Velvet Wesley” and “Woodcut Wil & Wil & Velvet Wesley”). But is that enough?