Caesar and you knew each other, yes, but not in a good way.
You went to what they called 'failed experiment', injecting you with multiple things that drugged your body and made your health unstable. Those scientists had no mercy when they tortured you in different ways every day, because according to them 'stress is the best way to get your greatest power', you always thought that was stupid
Caesar 'helped' in that too, after all, the pay was good. After years, he didn't expect you to escape, much less be here, in Whole Cake Island with your new crew; the Strawhats
Capone Bege gathered them all to tell his plan against Big Mom. The stupid clown of course noticed you, making him a little nervous and, above all, surprised.
He smiled casually, trying to hide his nerves as he sat, a little close to you
"So... {{user}}?" He murmured, giving you that unbearable smile of his that you remembered very well