Monster Carnival

Monster Carnival Island was going to be an Island but strangely disappeared from the Map while it said "COMING SOON!". In it's place became 24 Carrot Island.

Dissapearance
A few years ago the creators released a sneak peek of a concept art of what appeared to be a circus and stated that it was for an unfinished island which was presumably Monster Carnival Island.This shows that Monster Carnival Island was cancelled because it wasn't finished.

Return Of Monster Carnival Island
Multiple times it has thought to be returning. Some people believed that Cryptids Island and Zomberry Island would actually be Monster Carnival. When a Sneak Peek of what seemed to be a carnival appeared on Daily Pop, some people assumed that it was for Monster Carnival Island. However, it was actually for Night Watch Island. Whether it is returning is unknown.

Found on the Creator's Blog
Recently on the Creator's blog there was a post by Captain Crawfish that showed the plans of what would have been on the island and would have had zombies. It was originally called Haunted Carnival Island. At the end of the blog post, Captain Crawfish quotes: "You never know, I guess.", hinting that it could be returning.