Neither have I, but me and my friend would constantly say yipyipyip and we still do as an inside joke. So they've always stuck with me, it wasn't until someone request that I draw one that I realized it would be a great Halloween costume.
Haha, may not be the best costume for me~
It would only make it more tempting to annoy people by sneaking up on them and yelling "YIIIIIP!!" at the top of my lungs to try and startle them into dropping their candy, huehuehue~