Changes

*Early TV shows were live broadcasts which were not recorded for posterity; such a practice did not become commonplace until the 1950s, beginning with the use of kinescopes and then made popular by the decision of Desi Arnaz to film and preserve the episodes of his and his then-wife Lucille Ball's series ''I Love Lucy'' to sell as off-network reruns to local stations after their initial airings on CBS.

*Early TV shows were live broadcasts which were not recorded for posterity; such a practice did not become commonplace until the 1950s, beginning with the use of kinescopes and then made popular by the decision of Desi Arnaz to film and preserve the episodes of his and his then-wife Lucille Ball's series ''I Love Lucy'' to sell as off-network reruns to local stations after their initial airings on CBS.

*Some episodes may be lost due to the original master film or videotape elements having either disappeared (including through theft, as happened to the master film elements of syndicated animated series ''Colonel Bleep'', which disappeared in the early 1970s when, while the masters and other material belonging to show producer Soundac Studios was being moved into a van for relocation, the van containing the masters was stolen by car thieves and the Soundac material was never recovered), been misplaced, disposed of, recorded over (in the case of videotapes, for reuse of the tapes and because of the then-held belief that some types of programs, such as game shows, would not have continued commercial value) or deteriorated due to improper storage and handling or age.

*Some episodes may be lost due to the original master film or videotape elements experiencing the following fates:

:*Disappearence (including through theft, as happened to the master film elements of syndicated animated series ''Colonel Bleep'', which disappeared in the early 1970s when, while the masters and other material belonging to show producer Soundac Studios was being moved into a van for relocation, the van containing the masters was stolen by car thieves and the Soundac material was never recovered);

:*Being disposed of (as was the fate of a majority of the kinescope archive of the DuMont Television Network, which had been disposed of by a successor owner into the East River in New York City in the early 1970s, and as happened to early black-and-white TV series whose film elements were disposed of to recover the film reels' silver content via a silver reclaiming process);

:*Being recorded over (in the case of videotapes, for reuse of the tapes and because of the then-held belief that some types of programs, such as game shows, would not have continued commercial value); or

:*Deterioration due to improper storage and handling or age.

*Some episodes, despite still existing, may be withheld from syndication due to controversial content (such as "Bored, She Hung Herself", a second-season episode of the original ''Hawaii Five-O'' series, which only aired once on CBS and was pulled from further airings, as well as being excluded from home media, downloading and streaming release by distributor CBS Media Ventures after a viewer of the episode died as a result of imitating a dangerous yoga technique involving asphyxiation that had been featured in the episode).

*Some episodes, despite still existing, may be withheld from syndication due to controversial content (such as "Bored, She Hung Herself", a second-season episode of the original ''Hawaii Five-O'' series, which only aired once on CBS and was pulled from further airings, as well as being excluded from home media, downloading and streaming release by distributor CBS Media Ventures after a viewer of the episode died as a result of imitating a dangerous yoga technique involving asphyxiation that had been featured in the episode).

*Some series packages that were initially produced in black-and-white before transitioning to color production may air only the color episodes while withholding the black-and-white episodes due to distributor perception that the black-and-white episodes may not be as popular as the color episodes (conversely, in the case of ''The Andy Griffith Show'', only the black-and-white episodes from the show's first five seasons are currently aired in off-network reruns due to a perceived lack of popularity of the later color episodes).

*Some series packages that were initially produced in black-and-white before transitioning to color production may air only the color episodes while withholding the black-and-white episodes due to distributor perception that the black-and-white episodes may not be as popular as the color episodes (conversely, in the case of ''The Andy Griffith Show'', only the black-and-white episodes from the show's first five seasons are currently aired in off-network reruns due to a perceived lack of popularity of the later color episodes).