Goombas
The Goombas are a subspecies of the Toadstools; aggressive, dim, and obedient. As the centuries went on with the war between the Toadstools and the Koopas, the Goombas were used as cannon fodder in the name of the Mushroom Kingdom. Tired of being lowly foot soldiers without the promise of future equality, they were easily swayed to the opposite side. They are considered traitors in the eyes of the Toadstools and exterminated whenever possible. Most are simple beings with sharp teeth, but with the sorcerers' help, some have developed wings and have taken flight. They are even willing to enlist their children as soldiers in the great war, believing their sacrifices are for the greater good and a brighter future.
Koopa Troopers
The Koopas have had a long time to evolve and thin out the weak from the herd. However, 'intelligent' is not always a superior trait. Most of the Koopa species are barely smarter than the Goombas, but their ability to adapt is impressive, and their strength is unparalleled. Of course there are Koopas who can argue philosophy with the best of the Toadstools, but the Koopa Troopers are definitely not of such stock. Like the Goombas, the sorcerers have been able to give a number of them wings. Others have mastered small air spells and attack from the skies while sitting upon clouds.
Piranah Plants
The Piranah Plants are a semi-sentient, carnivorous weed that take residence in the many green transport tubes found all over the Mushroom Lands. Once they take root, anything short of death will never remove them. The Koopas purposely plant their seeds in specific tubes to prevent the Toadstools from invading secret layers and looting treasures. Some of these plants have been known to have been tamed, and some even show signs of affection for their owners.
Beetles
Beetles are very close in mentality to guard dogs. They can be trained to guard doors, tunnels, castles, anything really. There are two species: Blue Shells and Thornys. Blue Shells are quite loyal, and they quickly form emotional bonds to their owners. Other than their tendency to attack intruders, they are very good family pets. Thornys are still feral, and they only respond to pain. Teaching them anything is barely worth it.
Aquatic Life Forms
Although the rule of both Kingdoms is great, neither has gained a foothold on the open seas of the Mushroomlands. There isn't a competing ruler hidden in the depths (or so it is believed), but many creatures of the deep attack Toadstools and Koopas first and never ask questions later. The most aggressive of all the species are the Bloopers, who seem to have an alien intellect that helps them locate and kill any trespassers into their waters. The larger ones are always female, and they are constantly birthing new Bloopers fully formed and maturated.
Ammunitions
There are a few odd technologies that have stood the test of time. Specifically, there are three worthy of noting above all others, as they seem to be used in battles the most. Bob-Om's are a mobile bomb that will track down targets on land, and then they silently sneak up and explode without warning. Bullet Bills also track down targets, but their lifespans are short. To make up for this, they can fly through the air. The last is an interesting one. Unlike the others, the Chain Chomp is not an explosive. Rather it is a rabid creature used as a guardsman of sorts. It's tail (which is a chain) is pinned down into the ground, preventing it from doing anything but attack within a limited radius. Like Piranha Plants, Chain Chomps have been known to show affection to whatever brave souls claim themselves as the creatures' owners.
DEsert Scavengers
The deserts of the Mushroomlands are an odd mixture of lifeless seas of sands and small dots of blooming life. The Desertlands take up the majority of the blooming life areas, but there are still hints of life beyond the reach of the Mushroom Kingdom. There are three major species known to exist. The Angry Suns are an odd anomaly, as their entire bodies are engulfed with flame, yet they still retain the face of a living organism. Firesnakes have this unique ability too, although their sectional bodies suggest that they're actually an insect. The only truly sentient beings of the group are the Shy Guys, who hide their faces behind a white mask and cover the rest of their bodies in red cloth. Although the desert is their natural habitat, they haven't developed protection from sunburns. An odd flaw for a desert dwelling creature indeed.
Koopa Bros
Hailing from the respectable Moonsand District, there is a specialized military rank that the Koopas bestow only upon their strongest and bravest warriors; the Brotherhood. It has been within the Koopa tradition for ages that if a higher blooded Koopa reaches adulthood, he must prove himself/herself worthy in the battlefield under the banner of the Brotherhood. There are four sects total: The Hammer, The Boomerang, The Great Hammer, and the Fireball. Each sect specializes in the weapon of their namesake, and they are all terrifying. The Hammer is the most numerous, as their weapon requires the least amount of discipline. The Boomerang is specialized in surprise attacks and are responsible for guarding treasures. The Great Hammer is for Koopas who are great in size and stature, and they're mostly stationed around royalty and the castles. The Fireball is the rarest, as their unique physical talent is derived from the sorcerers. They are exterminators by nature, and they destroy everything in their path.
The Undead
Although rare, the undead creatures of the night are quite terrifying and spread fear into the hearts of the living. The Boos are the most numerous, and they tend to haunt abandoned castles, temples, and ships en mass. It is rare to see only one by itself. Their forms are malleable, and they have been known to stretch out to form "ghost bricks" that stretch out and attack passerbys. Dry Bones are Koopas resurrected from their shallow graves. No one knows who is doing this, and these mindless creatures are not talking. The living Koopas see them as failures, but they accept these slow undying creatures with a grain of salt. Dry Bones are generally only allowed to protect castles and dungeons, as the general public would create a large fuss over them.
Dungeon Inhabitants
Every castle is a testament to the surviving technology of the ancients. They harbor terrifying beings of magic and science, scaring away even the bravest of explorers. Some have apparently "living flames" that love to jump out of lava and hit random victims for fun. Others have red, impenetrable spheres that create sharp electronic discs to rotate around it. A few are even lucky enough to have Thwomps: living stone beings with the ability to levitate. Every one of the castles controlled by the Koopas has at least a sorcerer or two stationed there for the purpose of studying these anomalies and hopefully learning how to create more. They are called Magikoopas, and their wands can create illusions, magics, and summon other Koopas from thin air. They all must answer to Kamek, but only a few are ever lucky enough to become a member of the Black Shell.