As a photojournalism student in college, I had to take Micro Economics. I wasn't particularly interested in the subject, so I took a three week condensed course over the summer. Because I had nothing better to do all summer than sit in a stuffy lecture hall. Anyway, I remember nothing from the class - including whether the professor was male or female - except for the Law of Diminishing Marginal Utility. The law states that the first unit of consumption yields more utility than subsequent units. In other words, the first cookie always tastes the best.
The other thing I got from that class was the start of a story that I didn't write for another 5 or 6 years. It's the one I'm querying now. I had this scene in my head of a boy with a penchant for fighting with supernatural baddies slipping into his house after a fight and attempting to clean up before his mom discovered the damage. That scene spilled onto the pages of my notebook and now, almost a decade later, is the opening scene of a manuscript I'm really proud of. In fact, that open just landed me a spot as one of five finalists for The Reading Room's Aspiring Writers Competition. (You can read the scene & vote for me if you feel so inclined...)
You never know where inspiration will come from or when a random thought will spark something great. Small ideas can take root and grow into wonderful things. Never discount something because you don't have a place for it. Write things down, keep them for later. Let them germinate and blossom when the time is right. Ideas, unlike cookies, don't diminish with use.