The Porygon Fiasco
Strobe effects in EP038 lead to an unplanned four month hiatus of the
Pokémon anime. Due to this two winter specials were skipped
over (they eventually made it to air in the Fall of 1998), and a PSA
was created to explain the incident.
Therefore in order to fix the continuity, the two specials get placed immediately after the PSA.
Source: Bulbapedia