1901
Early 1985 promotional Super Mario Bros. sticker from Japan. Due to being released concurrently with the game, the drawings were made before the box art designs were finalized and thus use designs more closely based on the in-game sprites, like this Princess Peach design.
1902
In the VS. COM mode of the SNES version of Wario's Woods, every character has their name written normally, including both Toad and all opponents, with the exception of Wario, whose name is in all caps.
1903
Illustration from an article speculating on potential future Mario games from the Spanish Hobby Consolas magazine, showing a concept of a cooking game called Mario World Pizzeria. The drawing includes a cameo appearance of Raphael from the Teenage Mutant Ninja Turtles.
1904
Set of unlicensed Mario keychains. Note that Yoshi is either a) using a Boo item while not inside a kart, which has not yet been possible in any Mario game; or b) simply holding a very small Boo.
1905
From Charles Martinet's personal collection of fan mail.
1906
In Super Mario Galaxy, Mario's silhouette is visible whenever Mario walks behind an object. The silhouette is always of regular Mario, even when he is in a different form, like Bee Mario. To prevent too much of a discrepancy between the two models, Boo Mario has no silhouette.
1907
In Paper Mario: TTYD, entering a building and then clipping back out lets Mario walk around the area with most graphics unloaded, but the collision still present. Talking to NPCs will make the tail of the speech bubble point at Mario, making it appear as though he was speaking.
1908
Paper Mario uses a perspective trick to display the windmill in Gusty Gulch properly. While the blades appear attached to the mill in an ordinary manner during gameplay (left), they are actually floating in front of it (right) to prevent them from clipping into the building.
1909
Officially licensed Yoshi's Island figurine of Baby Mario.
1910
My apologies for an error in a recent Tweet. I had wrongfully stated that Luigi's skeleton can only be seen in cutscenes in Mario & Luigi: Superstar Saga, when in reality it can also be seen by failing the Thunder Bros. move. The Tweet in question has been deleted.
1911
Fan-submitted artwork from the British N-Force magazine.
1912
Yoshi's unobscured overworld sprites from Super Mario World/Super Mario Advance 2. These can normally never be seen in-game as Mario or Luigi are always riding Yoshi and partially covering him, but are actually saved separately from Mario and Luigi's sprites in the data.
1913
"Magnet Mario", one of the winners of a "design a Mario power-up" contest held by the British Computer and Video Games magazine.
1914
Unauthorized use of Mario artwork for a business in Nottingham, England.
1915
In Paper Mario: The Thousand-Year Door, the sprites of characters are layered in such a way that their face is only visible from the front. (Top: typical back view of characters.) The only overworld NPC with a double-sided face is the Lakitu reporter from Glitzville (bottom).
1916
Illustration from Game Players magazine that accompanies an article about Nintendo consoles outselling Sega consoles in 1994.
1917
Hooktail, the first chapter boss from Paper Mario: The Thousand-Year Door, seen from above. Due to only being intended to be viewed from the side, there is nothing covering the top of Hooktail's head, resulting in the tongue being visible.
1918
Concept art of the Toad Brigade from the official Super Mario Galaxy strategy guide by Prima.
1919
Left: concept art of alternate designs of mural enemies from Drybake Stadium in Paper Mario: Sticker Star. Upper right: some of the unused Mural Koopa designs still exist in the texture data. Bottom right: the final Mural Koopa designs battled in the game, for comparison.
1920
Update to the most recent Tweet: the photo was taken in Maryland, US in either 2001 or 2002. The information in my original post was taken from a Japanese blog. Thank you to @tristencitrine, the person cosplaying as Toad in the image, for the correction! twitter.com/MarioBrothBlog…
1921
In Super Mario World, if Mario has 99 lives and exits a level on the same frame he is touching a 1-Up Mushroom, his life counter on the overworld will indicate that he has "B0" lives. Upon entering another level, the lives display as 99 again.
1922
A call to all my readers: if you have access to the North American 3DS Virtual Console version of Super Mario Land, you may become the first person to prove the existence of the elusive Goombo. Details below.
1924
Mario and Luigi: Bowser's Inside Story contains a debug menu, accessible by modifying the game's code. In the Japanese version (left), all entries in the menu are individually labeled. The North American version (right) translates all of them with "no need to translate".
1925
The unreleased "Donkey Kong's Music Play" for the Famicom, shown in a 1983 Nintendo promotional handout. This screenshot shows the "Donkey Band" Karaoke mode.
Additional obscure Mario content for suppermariobroth.com.
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