Clefable is a tall, pink Pokémon with a vaguely star-shaped body. It has long, pointed ears with dark brown tips and black, oval eyes with wrinkles on either side. A curled lock of fur hangs over its forehead, much like its long, tightly curled tail. On its back is a pair of dark pink wings; each wing has three points. Its hands have three fingers each, and its feet have two clawed toes and dark pink soles.
Clefable is a timid, nocturnal creature that flees when it senses people approaching and is one of the world's rarest Pokémon. Its sensitive ears can distinctly hear a pin drop from half a mile to 1,100 yards away. Because of its acute hearing, it prefers to live in quiet, mountainous areas of which it is protective. It has also been seen at deserted lakes during a full moon. Using a bouncy gait, it can walk on water and sometimes appears to be flying using its small wings. The anime has shown that Clefable is actually an extraterrestrial Pokémon. According to one tradition, seeing a pair of Clefable ensures a happy marriage. Some scientists believe that Clefable stares intently at the moon because it is homesick. There is a legend to this as well, which tells of how it listens for the voices of its kind on the moon during clear and quiet nights.
In Clefairy and the Moon Stone, after the large group of Clefairy blasted Team Rocket away with Metronome, particles of the giant Moon Stone landed on some of them, causing them to evolve into Clefable. This also marked the debut of the species.
Multiple Clefable appeared for another Mt. Moon Festival in A Real Cleffa-Hanger along with a group of Clefairy, where they were trying to find a missing Cleffa. They later helped send Team Rocket blasting off.
Green had a Clefairy nicknamed Clefy, which first appeared in A Little Kadabra'll Do It. He later evolved into Clefable in The Winged Legends when Red used his Moon Stone on him. Although he was used only once for distraction against Sabrina prior to evolving, his increased power allowed him to stall Thu-Fi-Zer for a short time with his Metronome. He has since been used as a main member of her team in Green's battle against Lorelei. During the battle, he minimized himself to retrieve her miniature ice sculptures, deliberately blowing off the arm part to let the Elite Four's guard down. He has seen no major appearances since, despite always being listed as a team member.
Red's Clefairy can evolve into Clefable, although it has since devolved back to the Clefairy stage, as Pokémon can reverse the evolution process. Clefairy first evolves into Clefable in Clefairy Evolves... At Last?!.
The "Fairy Pokémon" category predates the introduction of the Fairy-type in Generation VI. From this generation onwards, the type and category of these four Pokémon share the same English name. However, this is not true in Japanese, where the type is フェアリータイプ Fairy-type and the category is ようせいポケモン Yōsei Pokémon.
Clefable seems to be based on fairies and pixies since it is a playful, magical, humanoid creature with wings. It may also be inspired by the concept of extraterrestrial life due to its rumored celestial origins and vaguely star-shaped body. It may also reference the mythical Moon rabbit due to its large ears, various Moon related powers, and the fact that it evolves from Clefairy using a Moon Stone.
Clefable may be a combination of clef (musical symbol) and fable.