<p>She's a wacky oldschool style Cartoon Character with elements of certain wacky DC Characters like Harley Quinn. Her elasticity is an obvious reference to various slapstick cartoons like Animaniacs. She has such a deep backstory relating to abandonment & incredible personality, what's not to love about Spinel?
</p><p>Also I don't understand how 1 can attribute her elastic properties to just Luffy, seeing as there are plenty of other characters with similar powers. Luffy wasn't even the 1st mainstream manga character to have that power interestingly enough with Dragonball giving powers like that to Majin Buu. Regardless I don't think her stretchyness really references Japanese series that much, instead being almost entirely in reference to American Made Cartoons & Comics.
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https://www.cbr.com/by-any-stretch-the-15-coolest-characters-with-elastic-powers/
</p><p>That only counts actual canon powers involving elasticity, meaning cartoon physics don't apply. A lot of Classic Cartoons had the wacky toon elasticity as part of the Cartoon Physics, especially in the old days. All of Spinel's movement in combat feels like a reference to that. I'm sure that there was an old cartoon where a scythe was swung much like how Spinel swings the Rejuvinator. I think videogames like Cuphead & a few others started the trend of returning to 1930's style in Cartoons artisticly which clearly played a role in Spinel's creation.
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