In chapter 931 we see Tama, Chopper, Momonosuke, and Kiku head to Kuri Beach. They then notice a massive person lying down on the beach, and after getting closer, Chopper realizes in horror that it is Big Mom.
Chopper quickly tries to get the rest of the group to be quiet and run away before she wakes up, but when he realizes that she likely came to Wano to pursue his crew, he quickly decides to kill her with his sword. However, the constant questions about Big Mom by the Wano natives cause Chopper to shout, resulting in Big Mom stirring. Chopper and Momonosuke quickly run away as Big Mom awakens, but Chopper is then stunned as Big Mom wonders who she is, having lost all of her memories.
Big Mom’s amnesia is definitely an interesting card for Oda to play.
One thing a lot of people don’t know about amnesia is that it can be caused by drowning or almost drowning as the brain is deprived of oxygen.
There are a ton of ways this could go, but I think the most likely is it will serve 3 purposes.
1-Big Mom will not be an enemy that the Straw Hats have no chance of opposing for right now. She is still super powerful and will retaliate against any attacks but for now, she’s not a loaded gun at the Straw Hats back.
2-Big Mom gaining her memory back will also probably tie into her past, if not with Caramel just yet, it will certainly explore her past with Kaido and the Rocks Pirates.
3-With Big Mom being stuck in a land where the food isn’t plentiful, there’s a good chance that she might have a hunger tantrum that can’t be solved with food. This would be a great opportunity for Chopper to shine and help cure that illness that’s she had since she was a kid.
Now the last point could be crucial into Big Mom forgiving the Straw Hats for ruining her wedding and possibly even convince her to join their cause or lend her aid to them either indirectly with her family or directly by walking up to Kaido and wailing him.
I do have some apprehension about Big Mom helping Luffy win by beating Kaido up so much that Luffy can hurt because I wanted him to be the strongest of whatever alliance but two Emperors fighting would be pretty badass anyways.
Furthermore, The Big Mom crew is spread out across Wano. Knowing they are in enemy territory, there is almost a guarentee that some may clash with Kaido’s crew and may need help. There are members of the Straw Hats that were not in Whole Cake who could help out and create new relationships with them.