Oda did not want Luffy to have a “cool” Devil Fruit power
Some fans of One Piece wondered why the main character received a power like rubber abilities – when there are so many “cooler” Devil Fruit powers. Eiichiro Oda answered this question himself in an SBS fan inquiry:
“I deliberately chose the silliest ability. If the protagonist were just strong and serious, I couldn’t have told this story for so long. Luffy is someone who stretches and inflates – even in serious moments, I can joke around with him. That’s exactly what this manga should be about.” (SBS, Vol. 65)
For Oda, humor is a central component of One Piece, and it should also be reflected in the fights. The rubber powers give Luffy the opportunity to fight in creative, silly, and unpredictable ways.
This idea reaches its peak with Gear 5, as in this form, Luffy is not only stronger than ever but also freer than ever. His movements no longer obey any real logic and function like in a cartoon.
With Gear 5, Luffy has reached a form in which he seemingly knows no limits – neither physically nor creatively. In this new stage, even the laws of nature no longer apply. And although this state resembles a cartoon, Gear 5 poses a serious threat to Luffy’s enemies: One Piece: Luffy has now become even stronger and resembles Tom and Jerry
