Just Weird

This article describes creatures and cryptids that are controversial or are just plain weird.

Prions
It was once thought that DNA was required for life. RNA viruses demonstrated that life can be made up of RNA. Prions are self-replicating proteins containing no nucleotides at all. The most famous prion was proven to be responsible for Mad Cow Disease (see https://en.wikipedia.org/wiki/Creutzfeldt%E2%80%93Jakob_disease), which created a public health concern in the 2000s. Prions resist normal disinfection techniques.

Wikipedia entry: https://en.wikipedia.org/wiki/Prion

Nanobacteria
Nanobacteria are alleged bacteria that are smaller than the generally-agreed-upon limits that are possible (about 400nm). Current research indicates that these are self-replicating crystal structures, which are not considered "life", but interesting nonetheless. They are thought to be responsible for the formation of kidney stones under zero gravity, which has been a health hazard for astronauts.

Wikipedia entry: https://en.wikipedia.org/wiki/Nanobacterium

Ultramicrobacteria
In early 2015, a paper was published in Nature describing bacteria that passed through a 200nm filter (http://www.sciencedaily.com/releases/2015/02/150227181339.htm), making the previous scientific consensus that the nanobacteria did not exist...moot.

Wikipedia entry: https://en.wikipedia.org/wiki/Ultramicrobacteria

Nanobes
Nanobes are tiny (as small as 20nm) structures that appear as fibers growing on rocks. There is an ongoing debate as to whether these are natural crystals or represent some unknown form of life.

Wikipedia entry: https://en.wikipedia.org/wiki/Nanobe

Martian Meteorite ALH84001
ALH84001 is a meteorite thought to originate from Mars found in Antarctica in 1984. It became briefly famous in 1996 when President Bill Clinton announced that life on Mars had been discovered by NASA. The meteorite was found to have microscopic tubes that NASA scientists interpreted as consistent with fossilized bacteria. This was ultimately met with skeptical rebuttals. The interpretation of these structures as fossils is still unresolved today.

Wikipedia entry: https://en.wikipedia.org/wiki/Allan_Hills_84001