I think I made it sometime during the shiggy craze. I created each frame in Paint Shop Pro 7 just using a simple cut around the mouth and painting around the eyes, changing things a little bit every frame. Then I used Jasc Animation Shop 3 to put 'em all together with its animation wizard, then exported the final product to a single .gif animation file. The Shiggy eek was inspired by the early Animutations with funny looking jaw drops and eyes popping out. I was also informed personally by Mr. Miyamoto himself that his jaw drops and eyes bug out in a cartoonish like manner when he is very surprised or startled.
User CP (left end of top menu bar)-> Edit Avatar -> Upload From Your Computer -> location of file. Just make sure that it meets the size requirements (can't be larger than 150x150 pixels and 390kb).
I don't mind if people on other forums use the Shiggy eek as long as they give credit to Tendo City. But in a realistic world I doubt many people will know where it originated. Anyway, I basically made it for Tendo City and donated it to these forums. So technically it's Ryan's property. :D
But your creation... and yeah, I doubt that the forums using it know (well maybe one person once did, but didn't cite where it came from or anything), or really care, where it's from... I'm sure we've done things like that too though, do we know the sources of all of our OTHER smilies? :)