Bdelloid Rotifers 

One of the coolest animalcules I first discovered with my microscope was the Bdelloid Rotifer. I couldn't get over the twin rotors sucking food into the rotifer's mouth. How interesting!
The name Rotifer comes from the Latin rota, "wheel", and -fer, "bearing"), and these are commonly called wheel animals or wheel animalcules. It's curious that the name "Bdella" is from the Greek meaning "leech".
Amazingly, in June 2021, biologists reported the restoration of bdelloid rotifers after being frozen for 24,000 years in the Siberian permafrost!
The coronal cilia (the wheels) create a current that sweeps food into the mouth. The mouth opens into a characteristic chewing pharynx (called the mastax), which has a powerful muscular wall and contains tiny, calcified, jaw-like structures called trophi, which incidentally are the only fossilizable parts of a rotifer.
They are found worldwide, in places where water is available - even if only temporarily. I found these in a plate of rainwater and debris in my yard.
Using a Tomlov DM202 Max, I observed them in a few drops of water held in a concave slide, so I was able to watch for a long time without the water evaporating. For some footage, I used above-slide lighting, to better see the colors on the specimen. No animalcules were harmed in this process (I returned them to the plate outside after filming!)
Original music/video "Smooth Drifter" by My-Fi Saloon @my-fisaloon8370