One Piece is an anime/manga that draws from the world of piracy. However, there are no characters in the work that possess the ability to stretch their mouths – a classic trait closely associated with pirates.
In reality, many of us are familiar with the names of pirates who stretch their mouths due to their infamous reputation. However, the truth is that the purpose of the mouth-stretching ability is not merely for show to conceal a hidden face but also serves to enhance and improve the strength of the character at night. This feature is essential for the dangerous work of pirates.

No character in One Piece stretches their mouth as a result of the creative intent of the author Eiichiro Oda. The creator of One Piece has also revealed the reasoning behind this particular trait.
Oda first introduced the concept of mouth-stretching pirates back in 2007, suggesting that there would be a character with this ability introduced at the end of One Piece . This is the reason why there are no other characters using this unique trait. This implies that the mysterious character could potentially be a very powerful and significant figure, as they will be the only pirate with the mouth-stretching ability.

Fans have speculated a lot about who this character might be. Theories suggest it could be either Luffy or Black Beard. In some early drafts of Oda’s ideas, Black Beard was initially envisioned with a mouth-stretching ability. Oda also acknowledged the connection between this ability and the classic pirate imagery.
Moreover, the concept of Luffy stretching his mouth carries significant symbolic value. This is because Luffy has always aspired to become the Pirate King. Therefore, the mouth-stretching ability symbolizes his journey and aspirations.
Up until now, the appearance of a character with this unique mouth-stretching ability remains a highly anticipated moment among fans, hinting at a climactic twist within the narrative.