Aliens are of yet unconfirmed species that may or may not exist outside of Earth.
Aliens have not appeared officially and are mostly regarded as fiction. Those who believed in aliens are seen as delusional or mentally unstable. Aliens are generally believed to be small grey men with big black eyes.
A leprechaun known as Wayne Whittaker posed as a UFO-specialist after being summoned to Earth. His kin, the fairies, began kidnapping all first-born sons in an incident that was believed to be the result of alien abductions. The abductions also led to a gathering of UFO watchers, one of them being Sparrow Jennings.
- Season 2
- Season 6
- Clap Your Hands If You Believe (mentioned only)
- Season 8
- A Little Slice of Kevin (mentioned only)
- Season 10
- About a Boy (mentioned only)
- Season 11
- The Chitters (mentioned only)
- Bobby Singer's Guide to Hunting (non-canon, mentioned only)
- According to Eric Kripke, there are no such thing as aliens in the Supernatural universe.
- The Alien dancing with Curtis was portrayed by Matreya Fedor.
- The beings Yokoth and Glythur from the Season 13 episode The Thing are modeled after the old gods of H.P. Lovecraft's work. While aliens are unconfirmed to exist in the main universe despite many hints that there's more to the universe beyond Earth, Yokoth and Glythur consumed entire galaxies in their universe, making them the closest things to aliens so far in Supernatural.