"Pilot, Part 1" follows the immediate aftermath of Oceanic Flight 815 crashing on a mysterious island. It focuses on Jack Shephard leading the survivors and the discovery of the plane’s cockpit in the jungle.
While not officially split into "Part 1," the first episode, titled " Romance Dawn ," introduces Monkey D. Luffy and his quest to become King of the Pirates. He meets Koby and faces off against Captain Alvida. Episode 1 | One Piece Wiki | Fandom
If you were referring to other popular series with iconic two-part pilots or segments: