Schoolyard Safari (found Nickelodeon short series; 2002-2003)
Date found: Dec 2015
Found by: AnimatronicPony
Schoolyard Safari is a series of 1-minute long animated shorts that aired on Nickelodeon (and later Nicktoons TV), hosted by a kid calling himself "Jungle Jim" who treated a regular school day as though it were a big safari expedition. In particular, he documents the boys at the supposed school he goes to. At the end, he ends the short with the catchphrase "Remember; it's a jungle out there!".
Initially, only five shorts had been uploaded to the internet, and funnyazhellanimation.com (the creators) stated that there were six produced. Some people also remember seeing this series dubbed in Portuguese, on Nickelodeon Brazil.
The reason that this particular short series was speculated to not get uploaded in full is likely because Nicktoons TV was not in the basic cable package at the time these shorts were aired. Therefore, it was unlikely anyone that wanted to was able to record them. It is also likely that Nickelodeon has forgotten about the series (a similar hypothesis has been brought forward with another series of lost Nickelodeon shorts, Astrology with Squidward.
Until recently, the series wasn't available in full anywhere on the internet. In December of 2015, the series was found in full and mirrored onto YouTube by user AnimatronicPony.