Characters' appearances on volume covers generally reflect their narrative importance in those story arcs. Luffy is far ahead of the rest, but Zoro does rank as No. 2. In Chopper's case, I think he's so high because he's the mascot, lol. Zoro is the second most globally popular One Piece character for a reason.
Volume Covers Featuring These Characters:
Zoro has 35 total appearances.
- Volumes: 1, 3, 5, 6, 9, 11, 12, 18, 22, 23, 26, 28, 32, 37, 39, 43, 49, 50, 51, 52, 61, 63, 64, 69, 71, 75, 76, 78, 91, 92, 93, 100, 102, 106, 111
- Debuted in Volume 1.
Sanji has 32 total appearances.
- Volumes: 7, 9, 11, 12, 17, 18, 22, 23, 26, 31, 32, 38, 43, 49, 52, 61, 62, 64, 67, 71, 73, 81, 84, 86, 88, 91, 93, 100, 102, 106, 108, 111
- Debuted in Volume 5.
Usopp has 31 total appearances.
- Volumes: 4, 6, 9, 11, 12, 15, 18, 19, 22, 23, 26, 32, 35, 38, 41, 43, 46, 49, 52, 61, 64, 70, 72, 74, 76, 78, 91, 92, 99, 106, 111
- Debuted in Volume 3.
Nami has 30 total appearances.
- Volumes: 1, 5, 6, 9, 11, 12, 18, 22, 23, 26, 32, 37, 43, 46, 49, 50, 52, 61, 64, 67, 70, 73, 81, 82, 85, 88, 91, 101, 106, 111
- Debuted in Volume 1.
Chopper has 30 total appearances.
- Volumes: 16, 17, 18, 22, 23, 26, 28, 31, 32, 37, 43, 46, 49, 52, 61, 62, 64, 67, 69, 73, 81, 82, 85, 88, 91, 94, 95, 99, 106, 111
- Debuted in Volume 15.