Ever had an idea you were too busy watching cartoons and scarfing Lucky Charms to follow through on that totally made someone else a fortune? Post your examples in the comments! Here's mine:
(A small but possibly important caveat to the following story: I was not a programming major in college. My course of study was more along the lines of, "I'll decide on something soon, really, I promise!")
I was taking Introduction to Pascal, and discovered I had an aptitude for flowcharting and concise coding, as long as the assignment didn't require too much math (this became a problem later). As a result, I'd get my class work done fairly quickly, then spend the rest of my time in the computer lab farting around with silly stuff.
One of the things I cobbled together was a simple text-editing program with several pre-made templates for short-short stories (fairy tale, science fiction, love story, etc.) It would ask you to input a series of generic words (proper noun, verb, adjective, and so on), then insert them into the template you had chosen. Alternately, it would just insert words randomly into the template from a database that remembered all your previous entries. My friends and I thought the results were pretty hilarious.
...and several years later I realized I'd accidentally invented Mad Libs. AAAHHHHH!!!
Bonus Example: Weird Al Yankovic stole my album title! Not that I actually had an album, mind you, but still...