He called himself as “Mr. Prince” in Alabasta but who could guess he really is literally? It was just a made-up alias that made him cooler, right?
Looking back, I was just cheering on him and nothing more. No suspicions. Then his bounty poster after Enies Lobby in which it was not him but a different person happened. It became an infamous gag in the series. But who knew this gag was relevant to the later plot all along? Duval somehow gave Sanji a big favor lmao.
The last foreshadowing was his bounty poster after Dressrosa which only states “Alive”.
But what most of us overlooked was the fact that Sanji is from North Blue. Way back in Java, Sanji casually says he’s from North Blue and immediately the topic was naturally changed to divert us from that small piece of info. Like how can someone from North Blue be in East Blue? Unless he rode a marine ship or he has advanced technology to cross Calm Belt and Red Mountain.
There are lots of foreshadowing but I just listed those major ones. Also, there are still small details that can be a possible foreshadowing tool. One of it is Nami’s ability to predict the weather with 100% certainty. It’s already innate in her and she’s the only character in One Piece that has this ability. Maybe it will be explained later in the series on how did she acquire this rare power.
Oda really took time to instill these little details that were always overlooked. You’ll only notice these little details once you reread the series. Goda’s level of foreshadowing is amazing.
*Theory by jinepifunny