Adaptation Restoration

Over the past century or so of pop culture, viewers and readers have gotten used to watching bits and pieces of their favorite works disappear -- or worse, mutate unrecognizably -- as they progress through adaptation after adaptation.

But sometimes, when they least expect it, something they thought was forgotten unexpectedly returns when a writer or producer who Gets It goes back to the original source and retrieves it.

And sometimes the restored content never made it as far as the original work -- cut for reasons of space, or budget, or because a suit somewhere didn't like it. Known only by rumor and/or "What Might Have Been" speculations, it was thought to be Lost Forever -- until a new adaptation suddenly pulls it off the scrap heap and thrusts it onto the stage.

This trope covers all manner of content which may have been abandoned -- for good reasons or bad -- as a work moved from one medium to another (or before its first release), but which then reappears unexpectedly after a move to yet another medium.

Contrast Adaptation Distillation, Compressed Adaptation and (when a result of removed scenes) Adaptation-Induced Plothole. A method of Adaptation Expansion. Compare Refitted for Sequel. The opposite in many ways of Adaptation Decay and What Might Have Been.

Anime and Manga

 * Pokémon Special includes the female trainer that was cut from Pokémon Red and Blue for cartridge space, but shows up in official art, as a major character.

Film

 * Many cut ideas, both filmed and unfilmed, made their way into the Star Wars Special Editions.

Literature

 * Novelizations of the Star Wars films include several deleted scenes. The Star Wars Expanded Universe has made repeated reference to events from deleted scenes like Luke's friends on Tatooine and talk of an "imperial academy" are the most frequently referenced.
 * The novelization of the original pilot film for the 1978 Battlestar Galactica includes material cut from or before filming, including the revelation that the Cylons were actually a race of Lizard Folk who used robots to fill out their military.

Radio

 * An official radio adaptation of Star Wars which was broadcast on NPR in the very early 1980s included the deleted scenes mentioned above in Literature, performed by the original cast and thus elevating them from apocrypha to Canon. (It also "revealed" that the famous Main Theme was nothing more than the inspiring background music from an advertisement for the Imperial Merchant Marine Academy.)

Video Games

 * The spell "Jolt" was originally cut from the Pathfinder book Ultimate Magic and released as unsupported unofficial content on the official blog. The spell was finally made official when it was included in Pathfinder: Kingmaker.