Cryptozoology certainly covers a lot of life forms & lots of people are curious about the multitude of various mysterious creatures.
http://animal.discovery.com/cryptozoology,
http://www.forteantimes.com/strangedays/cryptozoology,
http://www.unexplained-mysteries.com/search.php?cat=6
Perhaps some beings are able to pop in & out of this particular realm of existence.
http://desertshapes.blogspot.ca/2013/02/christopher-maloney-creatures.html
