*Note, this article leaves out any reference to the Yoshi's Island 2 (since it doesn't carry the Super Mario title), Mario and Luigi Superstar, Mario RPG, or Paper Mario series since I don't consider it part of the official Super Mario series. The games considered part of the Series here are the North American versions of: Super Mario Brothers, Super Mario Brothers 2, Super Mario Brothers 3, Super Mario World, Super Mario World 2: Yoshi's Island, Super Mario 64, Super Mario Sunshine, and Super Mario Galaxy.*
Yes yes, you all know that Mario 2 wasn't a real mario game. It was just Doki Doki Panic wrapped up in a Mario guise. It had Shyguys in it though, and these Shyguys have been in many of Mario's spinoff titles. Some may say that they didn't make an actual appearance in any real Mario game, but let me tell you that they did. Super Mario World 2: Yoshi's Island had many Shyguys in it, they were the most prevalent enemy type in this game. So the Shyguys were in two mario games, although you can contest that these were true mario games. Mario 2 was just a re-skinned version of Doki Doki Panic, and SMW2:Yoshi's Island was more of a Yoshi game, although it did contain the official name of a Super Mario World game. Using our knowledge of where Shyguys are in the network of Mario games we can come to a couple of conclusions.
First of all, Shyguys are old. They make an appearance in SMW:Yoshi's Island which showcases Mario, Luigi, and Bowser all as babies. This may also explain their appearance in Super Mario 2 since it was all just a *SPOILER* dream. This could just have been Mario remembering the Shyguys from his previous adventure as a child. Since they do not appear in any of the subsequent games we can also make another inference.
Since the Yoshi's Island game is strictly set on an island and this island is said to be the "home of all Yoshis" two different possibilities present themselves. The game Super Mario World has Yoshis featured across the games many stages. Though the game is called Super Mario World, the world map appears to be a series of islands that eventually become interconnected into one as you progress. So this may actually be the original island from Yoshi's Island since that Island claimed to be the "home of all Yoshis". The other possibility is that the Yoshis may have emigrated to new habitats, though Yoshi naval vessels have been absent from any Mario game (although they have kart technology apparently). We'll settle for the more plausible possibility of this being the original Yoshi's Island.
So where did all the Shyguys go since they did not make an appearance in the original Super Mario World that takes place after Yoshi's Island? If this is the island from that game, then the Shyguys should still be there. They may have possessed stilt technology and some could shoot bullets from their masks, but they seemed to be only a primitive tribal race of masked hooligans. This would lead one to believe that they didn't emigrate from the island through their own technology. From Bowser's appearance on the island in SMW2: Yoshi's Island and if this is the same island, it seems like he had conquered this land for his own. This may mean that he exterminated all the shyguys, forcefully relocated them, or they died out on their own. Either way, until the Shyguys make an official appearance in a series Super Mario game, they are MIA and I will miss them.
Hmmm...
I think a bigger question is where the heck is Wart. How many games have had him in it since SMB2? :p
In regards to your comment on Wart, there were many aspects and characters of that game that did not repeat in any other Mario game, probably due to the origin of our Super Mario 2. Birdo and Shyguy seem to be the only two characters to make regular appearances in other Mario spinoff games.
I don't remember Anti Guy and I played that game to death. The platforming inside the toy box was fantastic. General Guy and Gourmet Guy FTW.
Anti-Shyguy?
Perfectlyconfidentwithhimselfguy?
Dont try to tell him the Cake is a Lie