Marth Debuted in "Smash Bros.": Footage and music from Final Fantasy Type-0 is retained in the Western releases, despite that region not getting Type-0 till the HD remake in March 2015. And of course, there's "Somnus" from what was then Versus XIII and is now Final Fantasy XV appearing in the original game, although it's conspicuously absent in the iOS port and Curtain Call. Finally, a few tracks that were released as DLC are originally from games that never left Japan, such as "Megalomania" from Live A Live.
Highly feared at first, given the game's nature as one hell of a Widget Title. But then it was announced for the other regions. Averting such a trope is already a great feat for Square Enix, let alone the aforementioned nature of the game.
Played straight with the 3DS' DLCs in areas without Nintendo eShop Access (which is a rather huge chunk of Asia, parts of Africa, quite a few East European countries, and parts of South America that isn't Brazil).
Krile is the only DLC character not to be released outside of Japan, and Square has said they don't plan to release her. Why she remains exclusive to Japan is a mystery, but fans aren't happy about it. Apparently she's less important than having two Clouds and Auron with his arm in his sleeve.
As expected of a Japanese-developed arcade game, All-Star Carnival is Japan-only...mostly. It is available in Round 1 centers in the United States, complete with NESiCA network connectivity and functionality, but the interface is still in Japanese.
What Could Have Been: Theatrhythm was originally planned for the DS, but was moved to the 3DS due to greater storage capacity.