Mario games, like many others, are almost always released in Japan first. The programmers and game designers often base characters and events after their personal experiences, inside jokes, and sometimes even Japanese and American stories and fables. The finished game leaves many interesting things, which become more interesting the deeper you dive into it. Some things go unnoticed, while others leave you scratching your head. For example, "Who is Kuribo?", or "Since when is she 'Peach'?!". Read on, and this page might answer some of your unanswered questions.

Familiar names
Princess Toadstool has always been "Princess Peach" in Japan. The first game in America to use "Peach" was Yoshi's Safari, but the most noticed instance was in Super Mario 64, released three years later.

Goombas are known as "Kuribo" in Japan. Kuri means "chestnut," and bo could mean "people" (bo has a lot of meanings).

Bowser is always "Kuppa" (pronounced: Koopa) in Japan. Mario creator Shigeru Miyamoto revealed in an interview that they were considering naming Mario's nemesis either Kuppa, Yukke (Yukka), or Bibinbap (Bi Bim Bap), all Korean dishes.

Toad's Japanese name is "Kinopio," which comes from kinoko (mushroom).

Hinopio from Super Mario RPG is a combination of Kinopio (Toad's Japanese name) and hi (Japanese for "fire").

Waluigi: Nintendo Power magazine Vol. 135 (August 2000 issue) enlightened us with the fact that Waluigi's name "comes from a rearrangement of the word [ijiwaru]—Japanese for 'someone who's bad.'"

Wario's name is a combination of Mario and warui, which means "bad" in Japanese.

NokNok Shell (SMRPG) and Nokobon (SML) come from "Noko Noko," the Japanese name for Koopa Troopas. Incidentally, the Japanese word nokonoko means "unconcernedly."

Kamek, the Magikoopa, is a not just a clever name. Kame is the Japanese word for turtle. 

Luigi got his name from Nintendo of America.
Nintendo was trying to think of a name for Mario's brother, and there was a pizza parlor near NoA(Nintendo of America) called "Mario and Luigi's Pizza" so they named him Luigi.