This is a sort of game-like topic, but not for spamming. It's more of an informational thread to help enlighten other users. What you do is post Fiction - a commonly believed Mario myth and follow it up with Fact - what really is the truth. If need be, backing it up with sources. Since this thread is supposed to be informational, please leave discussion posts out unless you are refuting someone's facts. (Once refuted, Vorpal or I will remove said posts).
Fiction: Bowser has a relative (father?) named Morton or it is his middle name.
Fact: This is based on the seven Koopa Kids names, particularily Morton Jr. Koopa. People speculated that he was named after his grandfather, Bowser's middle name, or something of that extent. There is no actual foundation for this claim.
However, an interesting theory is that the koopa kids are all named after various famous people - most of them musicians. Though this is only readily apparent with Ludwig, this page offers a very plausible explanation for their naming scheme.
Fiction: Toad's real name is Kinopio Toad, or abbreviated Kinopio T. like in Paper Mario.
Fact: All the mushroom people are called a toads, a naming scheme introduced in Paper Mario. In the Japanese originals, all the people are called kinopios. Fans often will use the name 'Kinopio' to distinguish the toad from SMB2, SMRPG, and the sports games from all the other generic ones seen in other games. His official name is still just Toad and has not been changed by Nintendo. It's a generic name, but one that seems to be sticking.