I remember the description for Buzzy Beetle in the original Super Mario Bros. instruction booklet: “Quite the toughy, fireballs don’t even phase him.” They don’t work on Bullet Bills either, but for the most part, a fireproof enemy was a pretty big deal at that point. Although the name suggests they’re insects, they function a lot like Koopa Troopas, going inside their shells (which might or might not actually be shells) at one stomp.
If you won the game (which I’ve only ever seen on video, by the way), the second quest would replace all of the Goombas with Buzzy Beetles. Since the creatures don’t buzz, I figure “Buzzy” is a tough-guy sort of nickname.
Super Mario Bros. 3 confined most (if not all) of its Buzzy Beetles to underground levels, and gave them the ability to walk on the ceiling and drop off when Mario came near. It also brought in a few relatives, one of which was the Buster Beetle.
This dude had hands and would throw blocks at unsuspecting plumbers. Interestingly, it could be killed with a single stomp, and was not immune to fire.
Also in this game were the Para-Beetles, which Mario or Luigi could ride. They ended up only appearing in a single level in the Sky World, but the original game box pictured an axed stage which put them near ground level.
There was also data in the cartridge for a faster Para-Beetle that was green in color. Why these beetles ended up getting the short shrift, I don’t know.
Super Mario World brought in another monster of this type, the Bony Beetle, which was skeletal like a Dry Bones.
Wait, wouldn’t a beetle have an exoskeleton? Then again, there are also skeletal Piranha Plants in New Super Mario Bros. 2. Maybe these aren’t actually the skeletons OF such beings, but rather bones arranged in the shape of a Buzzy Beetle or Piranha Plant and then magically animated. Or perhaps Buzzy Beetles and their ilk aren’t really beetles at all, but rather an unknown species that look sort of like beetles, like how the sea horse just kind of resembles a horse. In Paper Mario: Sticker Star, the Bony Beetles look more like zombified Buzzy Beetles.
Finally, New Super Mario Bros. Wii was originally going to include giant Buzzy Beetles, but they were never used.
Interestingly, despite being a fixture in the series, I don’t think the cartoons ever featured Buzzy Beetles. There was an episode of the Super Mario Bros. Super Show cartoon in which Mario and Luigi were shrunk and chased by beetles that resembled the Beatles, so they might have been somewhat of a reference to Buzzy Beetles, but maybe not.
The Super Mario Bros. 3 cartoon had Para-Beetles show up a few times.