From Bulbapedia, the community-driven Pokémon encyclopedia.
A clip show is an episode of a particular series that is mostly made up of short segments from previous episodes, often to highlight what has happened during the series.
Primetime clip shows
From 1997 to 1999, 3 primetime Pokémon clip shows were planned. Only two of those have aired, with one being cancelled due to the Pokémon Shock incident. These clip shows ranged in length from an hour-and-a-half to two-hour-long installments, aired straight after the regular Pokémon episode of the week in Japan. They included many live-action segments. Much like Pocket Monsters Encore, the Weekly Pokémon Broadcasting Station, Pokémon Sunday and Pokémon Smash, they have not been aired outside of Japan.
Special clip shows
One clip show was planned to air by itself on a different day to the regular airing of the Pokémon anime. It was planned to air between Holiday Hi-Jynx and Snow Way Out!, but never aired due to the Porygon incident.
|| Aired because
|| 大晦日だよ！ ポケットモンスターアンコール
It's New Year's Eve! Pocket Monsters Encore
|| One hour special, planned to air on December 31, 1997, but eventually cancelled following the 1997 Porygon incident.
|| Content unknown
Regular broadcasting clip-shows
These clip shows have been released typically as the second episode of a one-hour special in Japan (though AG120 stood alone). They have been used to recap what has happened up to a certain point in the anime's current series. These have not aired outside of Japan.
|| Aired because
Satoshi and Haruka! Heated Battles of Houen!!
| March 24, 2005
|| As Ash and his friends approach Slateport City, site of the Hoenn Grand Festival, Ash remembers his Gym battles in the Hoenn region, while May remembers her Contest competitions.
|| Both Ash and May are about to compete in their regional goal, the Pokémon League and Grand Festival, respectively.
Satoshi and Hikari! Facing a New Adventure!!
| September 27, 2007
|| On their way to Hearthome City, Ash, Dawn, and Brock recall their adventures together so far.
|| Summarizes the first year of the Diamond & Pearl series.
The Mysterious Creatures, Pocket Monsters!
| March 26, 2009
|| The gang travels toward Snowpoint City, and along the way, remember what has happened so far in their adventure. Future events are also hinted towards.
|| Summarizes the Diamond & Pearl series so far, hints at near-future events including the reappearance of one of the Frontier Brains of the Kanto Battle Frontier.
Pocket Monsters TV Special: Masara Town Arc Recap episodes
Pocket Monsters TV Special: Masara Town Arc Recap is a series of three clip shows released as OVAs in 2000, available on rental-only VHS. They chronicled the events of the anime throughout Ash's Indigo League journey.