The Stage Complete fanfare plays when you collect one of the special treasures at the end of each stage, as well as when you discover one of the two hidden treasures. The title comes from the DuckTales: Remastered album, which matches the in-game title of the stage.
This is the original version of the song. It is track 13 in the NSF file and played on the RP2A03.
The Game Boy release features the same music as the NES, just in slightly lower quality. The song is played on the DMG-CPU B.
DuckTales: Remastered (W32)
This song was rearranged to pure digital music for the remastered game.