Not my fail, but a friend's. The most recent Pokemon game she had played was Platinum, and she really knew nothing about Generations V and VI. But after hearing about how awesome X and Y are, she decided to borrow another friend's copy of X last week. She was having a blast, especially since like, a third of the Pokemon she was encountering were completely new to her.
She was playing and Skyping with me at the same time, so she was a little distracted when she found a wild Swirlix. She told me how cute she thought it was, and I replied that I was planning to shiny hunt one. She asked what the shiny looked like, and by this time the wild Swirlix was long gone. I sent her a picture. She responded with profanity and tears, upon realizing that the one she just killed had been shiny.