You ever think about the fact that guys pretty much produce millions of tiny creatures that swim around inside them 24/7? Like obviously they can't feel them squirming around because they're so tiny, but just the idea seems freaky.
There are more E. coli bacteria in one single average human being's intestinal tract than there are human beings on planet Earth. Bacteria make up 60% of the non-water mass of human feces, and because of the importance of those bacteria to the environment of the human intestinal tract, a procedure called a "fecal transplant" has been developed. It is exactly what it sounds like.
Human skin flora are also extremely populous, and noticeable on a day to day level. Acne is just one product of human skin flora; human body odor, including non-offensive odors and an odor balance that seems distinctive of a particular person, are also largely bacterial products.
The importance of healthy vaginal and uterine flora are already well known to anyone on this site who actually cares for her hygiene, and the war against oral flora that we fight with toothbrushes, floss and mouthwash has been thoroughly explored, but there are also lung flora and ear flora.
Though by mass a human being is mostly human cells, by cell count a human being is in fact a bacterial hive. A normal person is home to 40 trillion bacteria.
This is, of course, not the limit of human symbiosis. A typical healthy human being is also the proud host of around 180 distinct species of fungi, particularly yeasts. I should not need to inform anyone on this site of the pervasiveness and health consequences of this particular cohabitation.
It should therefore be no surprise that not only is there a human virome, which includes proviruses (viruses whose entire viral genome is written into the DNA that is passed down across generations of humans and which are produced spontaneously by the organism as a consequence of their own DNA being read; viruses that are just as much "you" as your own red blood cells), but which also extends to viruses which never particularly interact with the human cells at all, and instead infect the 40 trillion bacteria and numerous fungi the body carries. When the human virome ravages the bacterial population of the intestine into a state of imbalance, a human fecal transplant may be recommended as a treatment.
Sperm aren't "creatures" really. Not any more than any other living cell in the human body.
We've just projected a lot of humanity onto sperm cells in particular because of their somewhat unique role of leaving the body and seeking out a specific target. It makes them seem more alive and sentient than other cells but they're not, they're just following their basic biological coding just like every cell in your body.
I know they're not literally "creatures," I just said that because they're motile and genetically distinct from their progenitor.
By this logic, cancer is considered a creature. It has unique dna and many forms are quite motile <3
Cancers are obviously creatures. Most cancers are capable of posting on imageboards, and a certain percentage of cancers make active contributions to open source projects.