Story Idea: Seeing Double

I just had the thought for a story, but I don't have the time this school term and I'm afraid the inspiration will go should it take to long to manifest. If anyone out there is interested, feel free to write about it but please mention it as my idea. Here goes:

Twilight has noticed subtle circumstances in town about seeing multiple ponies that look exactly (or almost) alike, and she tries to conduct experiments to find out the cause. Theories include: twins, changelings, clones, imps, moving (or teleporting) so fast they're in multiple places at once, the powers of a god to be able to do this actually, a mirage or advanced spell, Pinkie, and others. Everyone leaves her more and more frustrated because either it proves false or they just don't make sense. She eventually gives up.

A good pic for this would probably be a scene where the same pony appears numerous times in clear spots.

What do you think? Send me a reply if interested!