I'D SAY HE'S HOT ON OUR TAIL
From Chewiki: 1% Funny, 99% Hot Gas
I'D SAY HE'S HOT ON OUR TAIL (also known as Adventures of Super Mario Bros. 3 Remixed) is officially recognised as being the first YouTube Poop ever made by SuperYoshi on December 22, 2004. It has been remastered by mrSimon using a better quality picture source. It is so named by a quote said by Luigi, repeated several times for emphasis.
After installing Windows XP, SuperYoshi had noticed the program "Windows Movie Maker". He proceeded to test it by using an Adventures of Super Mario Bros. 3 episode, Recycled Koopa to be specific. Upon messing around with it a bit, adding annoying bits of repetition and the like, he uploaded it to Sheezyart. It was received well, and SuperYoshi proceeded to upload more of those videos, creating the mess we know as YouTube Poop.
Despite being the first YouTube Poop created, it was actually uploaded to YouTube a few years later, November 27, 2006 to be precise. The video that holds the distinction of "first poop to be available on YouTube" is "Sonic and Robotnik's Sodomy Hour!", uploaded on April 1, 2006.