Ebisu people all follow a philosophy of always being positive and constantly laugh about their troubles.
In reality, this is because they are unable to express any other emotions, no matter how they really feel, due to the effects of eating the leftover defective SMILE fruits.
Only one out of every ten SMILE fruits will successfully grant Zoan-like abilities. Thus, most people who consume one will not receive a power, and on top of losing the ability to swim, they become unable to express negative emotions, being forced to smile and laugh all of the time, although they can still shed tears. The defective fruits maintain this side effect even after being partially eaten.
The shogun of Wano Country, Kurozumi Orochi, took the leftover defective fruits and put them in the leftovers that the poor citizens eat in order to force them to express constant joy, with the intention of maintaining a visage of happiness around the country.
We all know Chopper’s dream is to find a way to cure any disease. Curing the people suffering from the side-effects of the SMILE at Ebisu would be the gateway to his dreams being achieved.
*Theory by HPsyche
