User blog comment:Kaido King of the Beasts/Three Things You Never Forget: 9.11, Harambe, and the Debt I Owe You/@comment-27930128-20160916134034/@comment-3507581-20160919041319

Like 12th Supernova said, it is a tribute to Kochikame (or Kochira Katsushika-ku kameari koen-mae Hashutsujo), which ended after 40 years of serialization and 200 volumes (it even became the recipient of a Guinness World Record for the Manga series with the highest number of volumes). It even got the cover in this week's issue -which is rare for a closing series in Jump-, and in it and in the opening color pages several Jump artists tributed its protagonist drawing him in their own styles. Besides, other artists paid tribute to Kochikame in their own series' chapters.

Said character is in the wanted poster; he's Kankichi Ryotsu (affectionately called Ryo-san), the main character, and the character Luffy wrote is in fact the well-known shape of Ryotsu's eyebrows.