The Koopas are not only an interesting Monarchy or Kingdom, but also a fascinating species in their own right. In a sense, the two features seem to be related, with members of the royal family being much larger, and having spiked shells, along with many other features that make them stronger. Observing the distinct variations in their appearance, even in the different areas of the same game, we can tell there is some difference in authorities amongst Koopa Troopas.

Green Troopas, being the weakest variety, are presumably infantry. Because Troopas with blue shells toss their shell at Mario in SMW, it is safe to assume that they are a type of guard, witch also makes sense because if you look carefully, they seem to be placed in crucial points in the area (near warp pipes or detours). The red-shelled Koopas are obviously smarter than green ones, as they do not walk off edges, possibly meaning they are a spy or scientist group. The yellow shell wielding Koopas seem to be a shock troop, because of their ability to switch on invincibility when climbing back into their shell.

Hammer Bros. also seem to have different spots in authority, although it would seem that they are their own authority all together. This is shown through the huge variances in the appearances of Hammer Bros. throughout the games, especially in SMB3 (witch will be explained most). The Fire Bros. and Giant Bros. are arguably the most dangerous, while the Boomerang Bros. are easily the weakest. I must say it is hard to place the differences in authority by using only their physical traits. Perhaps that is a matter for another time.

As for the "off beat" subspecies, such as the Buzzy Beetles, clearly these are very strangely evolved Koopas. The buzzy beetles seem to have evolved to fit their underground habitat, with the ability to climb ceilings, and their fireproof shells, possibly for use in surviving volcanically active periods. Spike tops would, of course, be even more highly evolved buzzy beetles. The lakitu and spiny. Interesting. Well, perhaps, since spinies are eggs in various games, a lakitu is an adult, female spiny, who out grew her shell in maturity, so she took a cloud or pipe as a form of protection. She would also use her children as weapons.