In Chapter 100, Buggy & Alvida were shown together, similar to Kaido & Big Mom. Not just that but Marco trapping Queen & King with his devil fruit is exactly like Smoker trapping Buggy & Alvida with his devil fruit.

Also Luffy repeated the same pose Shanks did in Chapter 01.

Luffy walking past Big Mom & Kaido is similar to Mereum passing Netero & Zeno & guess what is Mereum known as? “King”.

Even Luffy holding Kin’emon is similar to Netero holding Komugi & even him ordering Law is similar to Mereum ordering Pitou.

Luffy’s new Attack is named “Red Rock” and was aimed at a Pirate from “Rocks” Pirates. Since this is Dinosaur/Dragon themed Arc then it’s expected that Luffy’s Final Attack is King Kong + Red Hawk & will be called “Meteor”.

So we have:
Chapter 1 – Shanks Introduction
Chapter 100 – Dragon Introduction
Chapter 500 – Rayleigh Introduction (Also Kid, Killer & Law appeared in Chapter 500)
Chapter 1000 – Luffy Re-Introduction

*by Salah WG