(((OBVIOUSLY UNDER CONSRUCTION)))
The known multicelluar animal universe is basically broken into two rival familys that have been in virtual war for millenia - Team Protostome vs. Team Deuterostome. It's like the difference between day vs. night, male vs. female, cat vs. dog, happy vs. sad, baseball vs. cricket, or Coke vs. Pepsi.
The dividing line between the two rival faction of animals traces back to the beginning of mulitcellular life. It all begins with the question of - from which end should we start from? What should be create first - a mouth or anus?
Seems like an odd thing for a bitter divorce but since then the cooperative multicelluar life have been pepetually divided into two factions and has refused to speak to eachother ever since.
The animals that though it logical to build a mouth first became known to us a Team Protostome - or rather the mouthense. Their provisional name then called First Mouthers. This name would later be occulted by the human academic eleite in an ancinet wizardly tounge as "Proto-Stome" so common folk wouldn't get involved in the cosmic battle between First Mouthers and First Anals.
First Mouthers come in all shapes and sizes but the common trait is that they have absolutely no backbone or internal skellton. Rather if they have a skellton its always on the outside. This includes lady bugs, spiders, scorpions, octopi, squids and crabs.
From SpongeBob Squarepants land - Mr. Krabs, Gary, and Squidward Tentacles are a part of the Mouthenese Faction. While on the other side the First Butthole faction includes Patrick Star, Sandy Cheeks, Mrs. Puff and any fish for that matter (any animals with bones).
However there are a few multicelluar animals that refuse to take part in the battle between the Mouthenese and Bungholians. This would is where SpongeBob Squarepants comes in - he and his kind are neither Duerterostome or Protostome.
The group of creatures that though that the first opening on the body plan should have been a anus became known as the Deuterostome family line. If you are wondering which side we are on just remember that cosmic law are supposed to follow the laws of Deuteronomy. It may be a shock but our side of the animal family tree though the bung-hole was more a priority than the pie-hole.
The great thing about his revelation is that is proof positive that we do not live in a random universe and theory of evolution has flawed component about change being radom and rat race or competitive.
It makes us ask - Why hasn't any Protostome life form evolved an internal skelleton like a fish? Or rather - why hasn't a Deutrostome line evolved an external shell like bug? If natural events were random - you'd expect at least one Protostome life form to have an internal skellton analogous to fish and at least one Deutrostome life form to look like bug? But it just dosent' happen! Maybe long ago, but not now.
Are things as random as they really seem?