Hey guys! My english is not the best, so i will keep this theory short!
In the last chapter we got the informtion that emotions were stolen from some Wano people and the reason is besause of the smiles. So we can asume that you need stolen emotions to create smiles. Only happines wasn't stolen from the people. You can see the affected people only smiling. That would explain the name "smiles".
And it explains now the name of the SAD-tanks in Punk Hazard.
What is in the SAD-tanks? We saw Law destroying the tanks and we can clearly see some green liquid, which you need to create smiles. Those liquid could be those stolen negative emotions. Thats why it is called "SAD".
But why stolen emotions?
In chapter 184 we saw the first time an object with a devil fruit. Usopp stated "That's ridiculous. It's not as if the devil fruit has a will of its own." There are some theories that say, that devil fruits own a soul. I think this could be very true. The devil fruit-object fusion has a strong parallel with Big Moms soul ability to create homies. Giving a dead object a soul and it becomes a living thing.
For smiles you need emotions! It's like a lower version of a soul. But you can't steal happiness. Maybe thats the reason why smiles are incomplete and not quite work, like an original devil fruit.
Only Vegapunk was able to create one smile, that was working 100%. It was the smile that Momonosuke ate.
Now i come to the speculativ part, and it's very very speculativ, so don't be too hard to me
Momos smile worked perfectly. So which emotions could be in the artificially Fruit?
It's the perfect copy of Kaidos devil fruit. Could it be that Kaidos emotions were stolen from Vegapunk? Maybe that's the reason why Kaido has become such an asshole, because his happiness were stolen too. I know we saw Kaido with emotional outbursts and we saw him cry. That happens only when he's drunk. Could be a side-effect. I'm not sure about this, but i think it's worth to mention.
We have two strong connections between Vegapunk, Kaido and Big Mom.
We know that Vegapunk can study devil fruits and can turn it into technology. Like Kizarus lasers within the Pacifistas. What if Vegapunk studied Big Moms and Kaidos devil fruits in the past and thats the basis for his inventions. He could share a part of his past with Big Mom and Kaido and maybe had a connection with Rocks, where he was able lay his hands an those two.
- The devil fruit-object transfer is like the ability from Big Mom to create homies.
- Vegapunk invented the first smile, which is a copy of Kaidos devil fruit.
That could be the reason why Orochi wants Vegapunk from CP0 so badly.
We know that Vismoke Judge worked with Vegapunk. He did experiments on his own children to make them more powerful. The Vismoke siblibgs have now powers like Zoan Users, but they didn‘t lose their ability to swim. But they lost their emotions and emphaty, except Sanji. Could be connected with the smile-emotion topic.
What do you think guys?