"30303" turned upside-down is "EOEOE", which is realted to, but not the same as, "EIEIO".

"EIEIO" is the exclusive intellectual property of Old MacDonald Farms Inc. and is protected under various U.S. and international copyright provisions.

"EOEOE" is considered to be in the public domain and, thus, can be uttered without having to pay licensing fees to that money grubbing skinflint, Old MacDonald.