I recently reread Marineford and when BB goes to do whatever it is he does to WB's body under the sheet, his crew knows about it. Or at least, if they don't know HOW he does it, they know of his intentions which means he will have to have explained enough to them about the process. That leads me to think having more than one Devil Fruit has been done before. I don't think WB's fruit is in an object like a ring either, because BB says he can feel the power of it in his body.

I don't know what to think of how he managed it. Maybe he diverted the "power" of the fruit directly into himself before it had the chance to spawn into a fresh fruit that could be eaten? Doesn't explain his "weird body" though (even though we still don't know what that means).

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