These episodes were released to bridge the gap between the main anime series and the movie:
This episode, along with , makes up the Uta's Past Arc , establishing the childhood friendship between Luffy and Uta and setting the stage for the film's events. One Piece Film: Red Special Episodes One Piece Film: Red Episode 1
The official "Episode 1" for refers to Episode 1029: A Faint Memory! Luffy and the Red-Haired's Daughter Uta! which serves as the first tie-in prequel to the movie. These episodes were released to bridge the gap