Clefairy has appeared significantly in 4 episodes to date:
- Clefairy and the Moon Stone (EP006)
- Clefairy Tales (EP062)
- A Goldenrod Opportunity (EP158)
- A Real Cleffa-Hanger (AG134)
The relative low number of appearances demonstrates how elusive Clefairy is to see and catch in the context of the show. Most often, they are seen in the wild, and more likely at night than during the day.
In Clefairy and the Moon Stone, we meet the fairy Pokémon for the first time around Mt. Moon, in which a large extraterrestrial rock called the "Moon Stone" resides. This episode primarily revolves around Team Rocket's efforts to steal said Moon Stone for its rumored power, and how those efforts have disrupted the Pokémon living in the mountain (including a large group of Clefairy). This group of Clefairy is busily gathering pieces of a strange blue rock and carrying them all to a cave, seemingly ignoring the humans around them; when Ash and his friends follow, they find the Moon Stone, which begins to glow brightly blue as the last small stone is placed near it. The Clefairy dance around it happily, singing as if in worship...and then Team Rocket shows up!
Despite Ash & company's best efforts to defend the Clefairy's right to the Stone, it looks like Team Rocket might actually be successful for once, as they abscond underground with it...but soon, the Clefairy reveal how resilient they are, as they finally rebuff Team Rocket's efforts to take their beloved Stone once and for all with a surprisingly powerful attack resembling a Hyper Beam.
However, this attack shatters the Moon Stone into thousands of tiny pieces, which rain down on the group of Clefairy--and evolve those it strikes into Clefable! After this intriguing development, Ash and his friends are left wondering about the Pokémon's mysterious origins as the episode closes.
Clefairy Tales, however, shows a very different side of Clefairy's nature, as it takes place close to Viridian City, where many people are reporting items being stolen. And before too long, Ash & company experience thefts for themselves as well--including Pikachu! It turns out that a group of Clefairy are trying to build a spaceship to go back to outer space, and using whatever means they can to build it, even if it means stealing; they even stole Pikachu in order to power the ship. But their thefts seem not meant to harm anyone, only to provide them with what they need to return to their long-lost home.
The humans in this episode (both Ash & company and Team Rocket) seem utterly outclassed and outfoxed by the Clefairy; only Jigglypuff seems capable of matching them, and it quickly turns into a battle of the "cute pink plushie Pokémon" as Jigglypuff faces off against the Clefairy leader.
However, Jigglypuff's intervention disturbs the Clefairy's plans enough that when the timed launch sequence ends, the ship launches but loses a lot of its stolen cargo along the way. Pikachu is quickly found and reunited with Ash, and all the missing items are returned...but the ship doesn't make it out of orbit, which means it falls back to earth and the Clefairy have to start again in a new place, gathering more items for their mission.
Clefairy appears in a slightly more minor role in A Goldenrod Opportunity, starring as the favored Pokémon of Whitney, a young lady Ash & friends meet in Goldenrod City. (In fact, they meet her when Pikachu bumps into her Clefairy!) The gang is waiting for the Pokémon Gym to reopen the next day, so their original plan was to just kill some time in the city, but they had not been very successful at finding anything to do (or eat) thus far. With Whitney's help, though, they soon have a much better day. That is, until Team Rocket notices Whitney's Clefairy walking around with them and decides to make it a surprise gift for their boss!
Once Whitney realizes her Clefairy is gone, Ash & company look for and quickly find the lost Clefairy in Team Rocket's possession. The bumbling trio have tried to make their getaway on a monorail that isn't complete yet, and their foible buys the good guys enough time to catch up. At first it looks like Clefairy is going to be returned with very little fanfare, but Meowth takes the opportunity to swipe Pikachu instead! At Whitney's command, however, Clefairy uses Metronome, producing a Gust that sweeps Pikachu back out of Team Rocket's clutches, and of course, Team Rocket ends up blasting off again thanks to one indignant electric mouse. (In a surprise revelation, Ash & friends learn that they have been traveling with the long-sought Goldenrod City Gym Leader all day, and they have a friendly battle for a Plain Badge, in which Whitney reveals her fondness for her fairy Pokémon, not allowing it to get too hurt by battle.)
Lastly, in A Real Cleffa-Hanger, Clefairy appears briefly alongside its pre-evolved form Cleffa and its evolved form Clefable; the adventure surrounding them separates Ash's friends into two groups after Team Rocket's failed attempt at vacuuming up their Pokémon. (Cleffa ends up with Misty, Azurill, Max, and Ash's wounded Pikachu, while Clefairy and Clefable end up with Ash, Brock, and May.) During the course of this episode, the two groups finally reunite and fight Team Rocket's Pokémon theft attempts a second time, with the trio of fairy Pokémon providing both distraction (with Teeter Dance) and a surprise Solar Beam that finally sends Jessie, James, and Meowth blasting off again. Then Ash & company follow Cleffa, Clefairy, and Clefable to Mt. Moon, where they are able to witness the beautiful ritual moon dance of the Clefairy.