A ghost is popularly held to be the disembodied spirit or soul of a deceased person. Popularly described as insubstantial and partly transparent, ghosts are reported to haunt particular locations that they were associated with in life or at time of death. A revenant is a deceased person returning from the dead to haunt the living, either as a disembodied ghost or alternatively as an animated ("undead") corpse.

Phantom armies, ghost-animals, ghost trains and phantom ships have also been reported.

A poll conducted in 2003 showed that more than half of adults in the United States believe in ghosts and/or demons. To date, there is no solid empirical evidence of the existence of ghosts.

Ghosts or similar paranormal entities appear in film, theatre, and literature; legends and myths, and some religions.

Extraterrestrial life is life that exists and originates outside the planet Earth, the only place in the universe currently known by humans to support life. Its existence is still hypothetical as there is currently little, if any, evidence to indicate that other planets can support life, and there is no evidence of extraterrestrial life that has been widely accepted by the scientific community. Some, however, point to moons of Jupiter or other celestial bodies that might conceivably have some forms of life (bacterial or otherwise).

Most scientists believe that if extraterrestrial life exists, its evolution occurred independently, in different places. An alternative hypothesis, held by a minority, is panspermia. This suggests that life could have been created elsewhere and spread across the universe, between habitable planets. These two hypotheses are not mutually exclusive.

The putative study and theorisation of extraterrestrial life is known as astrobiology or xenobiology. Speculative forms of extraterrestrial life range from sapient beings to life at the scale of bacteria. Since no examples of confirmed extraterrestrial life are available for examination, these studies presently remain within the realm of speculation.

Bigfoot, also known as Sasquatch, is an alleged ape-like creature purportedly inhabiting forests, mainly in the Pacific Northwest region of North America. Bigfoot is usually described as a large, hairy, bipedal humanoid. Many believers in its existence contend that the same or similar creatures are found around the world under different regional names, most prominently the Yeti of the Himalayas.

The scientific community considers Bigfoot to be a combination of folklore, misidentification, and hoaxes, rather than a real creature.^[2] In general, mainstream scientific consensus does not support the posited existence of megafauna cryptids such as Bigfoot, because of the improbably large numbers necessary to maintain a breeding population^[3] and because climate and food supply issues would make such purported creatures' survival in reported habitats unlikely^[4]. Despite these facts, Bigfoot is one of the more famous examples of cryptids within the pseudoscience of cryptozoology.