One thing I love about space and science fiction is the incredible number of possibilities. We suspect the universe contains around a septillion stars -- 1,000,000,000,000,000,000,000,000. Even if we pessimistically assume one in every million stars contains a planet with life, that is still a quintillion planets -- 1,000,000,000,000,000,000 -- an unimaginable number of possible ecosystems.
The number is so great that if certain things are technically possible they become almost probable. Basically, any creature that we can imagine, as long as it obeys the basic laws of physics and would make at least some evolutionary sense, probably exists in some form, somewhere out there.
So on some distant planet, there is likely a species of animal that evolved to fill the same ecologic niche as equines and also have a single long horn for mating displays. There is a very good chance that in some alien forest, there are large, hairy bipeds walking around that look and act just like our mythical sasquatches. At this moment, there are probably large, scaly, winged creatures flying around looking for prey under a distant star which bear an incredible resemblance to dragons.
This is one of the things that has always drawn me science fiction over fantasy. While I won't live long enough to see if we ever find anything like the incredible creatures or worlds some of the greatest sci-fi authors have dreamed up, there is something magical knowing that probability suggests they may really exist in some form out there.
*Andromeda galaxy picture from NASA