The List of Implied Items is a list of items, objects, and foods that have not physically appeared up in any form of media to this point in time. Regardless of their lack of appearance, the implied items have been mentioned at least once throughout the Mario series.
Bowser Jewel
The Bowser Jewel is an item that Bowser mentions in Paper Mario: The Thousand Year Door. When in control of him between chapter 1 and 2, the player can make Bowser check the statues on the wall. At first, he will say "I got the Bowser Jewel!". Shortly afterward he will say "Just kidding". It is unknown if such an item exists.
Demented
Demented is Dimentio's personal brand of fragrance and perfume. In Chapter 8-3 of Super Paper Mario, Dimentio is confronted by Mario, Luigi and the Pixls. He informs them of his plan to betray Count Bleck and usurp the Chaos Heart, and, after forcing them to play a magical game of tag with him, he offers them a list of bribes. Among the other items in this list, Dimentio mentions a signed bottle of his perfume, claiming that, were Mario and Luigi to wear it, people would "stand in ovation whenever they enter a room". It is unknown if Dimentio merely fabricated this, or if he actually owns his own line of products. The same is true with Mimi's offer of a Pixl named Breadward.
Dramalama Plaque
The Dramalama Plaque is the prize for winning the Jazzafrazz Town Drama Slam, in Paper Mario: The Thousand-Year Door. As it happened, the Marvelous Compass piece that Luigi needed was embedded in the plaque. With the help of the Crazee Dayzee Hayzee, Luigi won the plaque and he could continue his journey.
Fat Dog
The Fat Dog is an implied item in Paper Mario: The Thousand-Year Door. The only mention of this item is when Mario gives the Ratooey Businessman his briefcase combination. The Ratooey says that his company and Hoggle's Hot Dog stand were going to join the Fat Dog and Hot Sauce into one product.
Flipside Tower Postcard
The Flipside Tower Postcard is an item offered by Skeet in Super Paper Mario for 1,000 Coins. It's a limited time offer. He only offers it between Worlds 2 to 3.
Mushroom Full Course
The Mushroom Full Course is the only known food served on the Excess Express (although there are assumed to be many other food items served on the train). It was only mentioned in Paper Mario: The Thousand-Year Door.
The Mushroom Full Course can first be mentioned in the afternoon of Mario's second day riding the Excess Express, shortly before its arrival at Riverside Station. Talking to Chef Shimi during this period of time will allow Mario to discover that he was currently working on a Mushroom Full Course meal for that night; Shimi would also list the Mushroom Full Course's courses when spoken to: Apparently, a Mushroom Full Course starts out with Mushroom bouillon, followed by Mushroom mousse, then Mushrooms in the spice saffron (not to be confused with the Saffron character from Super Paper Mario). A "delicate but puzzling" Mushroom sorbet is given as dessert in the Mushroom Full Course, which is ultimately ended with Mushroom coffee. Talking to Shimi that night would give the Mushroom Full Course another mention, in which he stated that he was serving it and that he had hand-picked the Mushrooms for use in that night's Mushroom Full Course at Riverside Station. (At this, Mario's partner would question the Mushrooms' edibility.) Talking to the Toad Waitress at the same basic time would trigger yet another mention of the Mushroom Full Course, in which the waitress would state that it was being served as they spoke before pondering why Chef Shimi always used Mushrooms in his meals. (Shimi's lack of culinary skill with anything but Mushrooms would become a bit of a recurring joke in Paper Mario: The Thousand-Year Door; a few other minor non-playable characters would go on to mention it in various ways.)
Shimi has claimed that it is his "super-duper specialty".
Nibble-Um
A Nibble-Um is a snack briefly mentioned in the game Super Paper Mario. When Francis is about to make Tiptron Mk. II, he orders his MeowMaids to bring him some Nibble-Ums, which seems to be a cheesy snack. Nibble-Ums are probably based on Cheez-Its, a cheesy snack in the Real World.
No-Itch Potion
No-Itch Potion is a substance which was only mentioned in The Super Mario Bros. Super Show! episode "Jungle Fever".
In "Jungle Fever", Butterfingers, the assistant of the famous witch doctor, Dr. Sheldon, attempts to create a batch of No-Itch Potion. Unfortunately, Butterfingers fails to create any No-Itch Potion, only creating some sort of duplication potion, meaning that Mario, Luigi and Toad, who were doused in King Koopa's Koopa Strength Itching Powder, could not be cured of their itchiness.
Poison 1-Up
A Poison 1-Up is a type of Poison Mushroom only implied in Super Paper Mario. When Mario goes to The Underwhere for the first time, a Shayde will ask Mario how he got a Game Over and begin listing him possible ways he could have died, such as falling in a Bottomless Pit. One of these ways was "eating a Poison 1-Up", which is therefore thought to be a poisonous 1-Up Mushroom. However, as stated before, a Poison 1-Up has never been seen in a Mario game, only mentioned. Also note that the Poison 1-Up may not even exist, and the game's writers made a mistake and confused a normal Poison Mushroom with this Poison 1-Up.
Reclinatron 4500
The "Reclinatron 4500" is a type of chair only mentioned in Super Paper Mario. When in Castle Bleck, Mimi, disguised as Merlee, will ask Mario three questions about what he hates the most. On the third question, one answer is "Francis". If the player selects this, Mimi will somehow teleport Francis to a room in the castle. When Mario enters this room, Francis is confused about why he is there, then decides that because he was thinking about Francine, his Reclinatron 4500 teleported him there. Francis then battles and loses to Mario.
Southern Fried Egg Dog of Tastiness
The Southern Fried Egg Dog of Tastiness was a Hot Dog that Mr. Hoggle was going to create out of a Hot Dog and a Southern Yoshi Egg in Paper Mario: The Thousand-Year Door. It was supposedly going to make fighters stronger and taste delicious. However, since Mario rescued the Yoshi Egg, this Hot Dog was never actually created, therefore, Mr. Hoggle could not sell it at his shop in Glitzville.
Super Mega Ultra Shroom
A Super Mega Ultra Shroom is a Mushroom that was mentioned by Mimi in Super Paper Mario. It may be assumed that there is no such mushroom as Mimi was disguised as Merlee and was offering various things (similar to Hooktail) to Mario and his party, claiming she would give him it along with the Pure Heart if they signed a contract to pay ten million Rubees.
Tongue-Blistering Fat Dog
The Tongue-Blistering Fat Dog is a cancelled product made by the Ratooey Businessman's company and Mr. Hoggle's Hot Dog business. It was briefly mentioned in Paper Mario: The Thousand-Year Door. After Mario got the Ratooey's briefcase combination, he walked over to the Hot Dog Stand and had a short discussion. He then told Mario that his new product was cancelled, the Tongue-Blistering Fat Dog. He said that it would be a combination of his company's Hot Sauce on Hoggle's Fat Dog, but the deal was not closed for unknown reasons.
Twilight Blade
The Twilight Blade is an item that Bowser mentions in Twilight Town of Paper Mario: The Thousand Year Door. When in control of him between chapter 4 and 5, the player can make Bowser search the area of grass to the left. At first, he will say "There's something in the grass!... I got the Twilight blade!". Shortly afterward he will say, "I'm just joking. Sucker." It is unknown if such an item exists.