Some, all, or no life on earth may be of extraterrestrial origin. Of course, we are all made of star stuff, so in this sense, being composed of the same elements of the cosmos, we are all of extraterrestrial origin. It is never a question of that we are so, but of when we became so.
Still there are some seemingly un-earthly life forms on earth, like geo-thermal-philes around volcanic vents, tube worms under the sea, and arsenic based bacteria from Mono Lake in California.
Weird and unearthly looking fungi, plants, insects and crustaceans have all been speculated upon as unlikely travelers from beyond.
But few people are interested in microorganisms or waving noodles under the sea. They want to know whose closets are hiding E.T. along side all the other stuffed animals?
They want to know if the super model they have a crush on is actually a Nordic alien with supernatural bikini, or bicep, powers.
Along with this speculation come the tales of all other “unearthly” beings such as ghosts, angels, leprechauns, demons,fairies, and a whole host of spirits from the forest dwelling, to the ocean depths, and forest, field, and stream.
It is not unusual, and completely expected that most people living close to the earth recognize such beings both in folklore and in animated in-dwelling “presence.” Many natives, including western cultural "pagans" accepted that human is not the sole intelligence on the planet.
The difference between superstition, creation myth, and sound recognition of evolved life forms are largely semantic. Even now, many sciences acknowledge the "life" of the river, the soil, or even the weather and fire.
Indeed, these sorts of belief systems are more prevalent than is realized. It does happen more often than not, however, that these beliefs when others have them are considered superstitious or absurd!
The strong desire to know our origins, combined with the longing to connect to a larger universe is what prompts this type of inquiries. This is what should be examined, why, how, and when, we became so disconnected from life on earth. Many today realize that modern humanity is alienated to all other life upon which it depends. This creates a severe cognitive dissonance, and although we want to pretend we are somehow superior to other life forms, both earthly and otherwise, we seem a bit lost in space.
Only modern humans forced to dwell in concrete, cubicle, and consumption are so truly disconnected to the earth that they assume such terrestrials are not a natural part of the integrated ecologies of earth.
Are some of the bizarre life forms found on earth possibly extraterrestrial? It is not likely, as life itself is now realized by science to not only be diverse, but to be wholly dependent upon evolving diversity and new mutations every day.