- Mario and Luigi are Italian, right? Nope. None of the games have ever stated this, and since Super Mario World 2: Yoshi's Island, they have explicitly been shown as natives of the Mushroom Kingdom.
- Mario is always viewed as using his head to smash blocks open in the games, which leads to people joking that Mario suffers brain damage or a similar injury by the end of the game. While not obvious at first, if one looks closely when Mario jumps, he raises a fist in the air as he jumps and his fist hits the block, not his head. Ironically, if Mario is using a power-up that lets him fly or he is holding something in his hands, he really does use his head to break the blocks, but this is usually due to lack of proper animations. In official media, Mario always uses his fist to hit blocks from underneath, though Luigi actually does bash blocks with his head in Super Mario All-Stars + Super Mario World.
- Many fan videos joke that the manual for Super Mario Bros. states all the blocks are Mushroom Kingdom citizens transformed into blocks and thus whenever Mario breaks a block, he's killing a citizen. The original manual actually says only the Power-Up Blocks are transformed citizens and they are noticeably completely indestructible within the game; in fact, they actually help him by giving out the various items they hide. Good luck getting that point across to the many people that believe that every single brick block is actually a Toad, and that Mario is a murderer for every ordinary brick block he breaks.
- Similarly, Mario does not "spit" fireballs after collecting a fire flower, he "throws" them from his hands. For that matter, he doesn't "eat" the mushrooms, fire flowers, leaves, etc. he encounters. Even as graphics continue to improve, Mario is still depicted as simply absorbing power-ups into his body when he "collects" them. note
- Everyone "knows" that Mario's original name was Jumpman, but it actually wasn't. Before the character debuted in Donkey Kong, Shigeru Miyamoto called him "Mr. Video" and planned to include him in various different video games as cameos. And even before that, artwork of the character was labelled "Ossan", which is Japanese for "middle-aged guy".
- Whenever Daisy's kingdom of Sarasaland is brought up, it is always said to be a kingdom that consists only of a desert. However, Sarasaland is made up of four different climates. Alongside the desert of Birabuto, there is the aquatic Muda Kingdom, Easton is made up of rocky terrain, and the Chai Kingdom is based on Ancient China.
- Everyone "knows" that Mario is abusive towards Yoshi, hitting the poor dinosaur on the head to make it attack his foes. In actuality, it only appears this way due to sprite limitations in Super Mario World; official artwork◊ has always depicted Mario pointing forward at their target, not smacking Yoshi, and this is how it has always been represented in more recent media◊ with higher-fidelity graphics. As for Mario dumping Yoshi down a Bottomless Pit just to save his own skin that is a purely player choice and there is no part of the game where that is required. In 2017, it was "confirmed" in an interview with Takashi Tezuka and Shigefumi Hino that Mario has always been hitting Yoshi on the head... except it wasn't confirmed at all. The interview actually reveals that this was the original intention, but it was changed during development to Mario telling Yoshi "Go!" to avoid making him seem abusive towards Yoshi. Unfortunately, misleading headlines in reports covering this interview only worsened the "Common Knowledge" effect.
- Mario is a middle aged man in many gamers' eyes. While this was true in very early titles - thus why Mario was played by older men in live action adaptations - it has long since changed. Mustaches tend to make people seem older after all. Mario is actually a very young man, barely older than Peach. In Super Smash Bros. Melee he's said to be 26, and Miyamoto stated in 2016 that Mario is currently considered to be 24 years old.
- The fandom clumps Rosalina, Peach, and Daisy into a trio of princesses. Canonically, however, Rosalina isn't royalty at all; she's consistently been referred to as "Rosalina", not "Princess Rosalina". Her crown is the cause of most of the trouble, possibly as an artifact from when she was planned to be related to Peach.
- Fanon often is confused for canon. There has never been a "Clawdia Koopa" (supposedly Bowser's ex and the mother of his children) mentioned in any official media; she is the creation of an early fansite. Daisy is also not Peach's cousin despite fans assuming otherwise; the strategy guide that mentioned them being related wasn't authorized by Nintendo.
- Whenever people bring up Super Mario Bros.: The Lost Levels, they mention how Nintendo refused to release the game due to its sheer difficulty. What people tend to forget is that A: Japanese gamers and critics also had a major bone to pick with the difficulty, and B: Nintendo of America wanted a different Mario game, and believed the sequel was simply just a copy of the first game, thus people wouldn't want to play the exact same game again with new tweaks.note
- Along similar lines, there's the myth that the game released as Super Mario Bros. 2 was a randomly chosen game given a graphic facelift. Doki Doki Panic was created by Shigeru Miyamoto, and had references to previous Mario games. It was changed to a licensed game for Fuji TV midway through the development process. In turn, it is sometimes claimed that Doki Doki Panic started development as a sequel to Super Mario Brothers. An old interview between Wired and director Kensuke Tanabe said Tanabe was assigned to do a prototype for a "Mario-style platformer focused around vertical levels" as his first job at Nintendo, but saying Doki Doki Panic was always intended to be a Mario game based on that is a leap of logic.
- The arcade version of Super Mario Bros., Vs. Super Mario Bros., does not have levels from The Lost Levels in it. The arcade game was made first, by many of the same people, and some levels were copied into the console sequel, so it's The Lost Levels which has Vs. levels in it, not the other way around.
- It's been stated matter-of-factly that the seven Koopalings were "based on" the creators of Super Mario Bros. 3. This comes from a somewhat clumsily-translated interview with Miyamoto in the Nintendo Power "Mario Mania" player's guide. Read in full context, it's clear that Miyamoto is saying the various creators of Mario 3 each got to design their own Koopaling, not that the Koopalings were based on themselves in some way. This explains why none of the Koopalings really "match" each other, from a design perspective, and why there is a female one, despite the fact that no women were part of the design team.
- There's a portion of the fanbase that believes Bowser used his Japanese name of Koopa in the NES games. With one tiny blip, this isn't the case; the name Bowser goes all the way back to the instruction manual for his debut, Super Mario Bros. While he was called Koopa in the cartoons and movie, English translations of the games have consistently called him Bowser, with the exception of Super Mario Bros. 3, which does indeed call him Koopa in English.
- One fact that tends to come up in Alternative Character Interpretations of Mario being less than heroic, or straight up evil, is that he stomps on enemies that are beyond harmless, like Goombas, who don't even try to attack Mario, they just mind their own business and walk in pre-determined paths, the only danger being from running into them. It is true that in the original game and other old 2D platformers, technical limitations made it so that enemies couldn't have complex attack patterns, so they simply walked back and forth, acting more like obstacles. In modern 3D platformers, and in spin-offs like the various RPGs, though, it's made clear that the Goombas that work for Bowser aren't simply "minding their own business" and they do actively try to attack Mario. The same can be said about basic Koopas.
- Luigi is often treated as the poster child for put-upon little brothers, with Mario being a Big Brother Bully. This seems to come from people misinterpreting or misunderstanding Luigi's Second Banana Complex. Mario's not a glory hound who forces Luigi out of the spotlight because he can't share it. As a matter of fact, Mario is just about the only person who actually appreciates Luigi. Luigi's issues instead stem from the fact that everybody else puts the spotlight solely on Mario, ignoring him and his accomplishments, even if he was right there alongside Mario to help. Luigi's cowardly personality also means he tends to prefer being safe at home than going on adventures, often being dragged into his latest adventure against his will, so it may even be that he actually prefers Mario to be in the spotlight.
- This track from Mario Golf for the Nintendo 64 is almost exclusively referred to as "Dormie". However, not only does it play when a player has one hole left to win in Match Play/Get Character regardless of whether or not it's a Dormie, but it plays on the last hole in all other multiplayer modes.
- Mario and Princess Peach are a couple. Though it varies, most media present them as not actually dating yet. They're flirty but are not going steady.
Common Knowledge / Super Mario Bros.