Update: Fils-Aime said that the demo would be available in Apple Stores this Thursday, not the app store as originally reported. The article has been updated accordingly.
A few moments ago, Nintendo of America's president Reggie Fils-Aime joined late night talk show host Jimmy Fallon to showcase Super Mario Run, the upcoming mobile auto-scroller from Nintendo. Fallon got his hands on the game a little early, and with Reggie's help, completed one of the game's levels. Though the full game launches on December 15th, Reggie also announced that a demo would be coming to Apple Stores later today. If you're unsure about Super Mario Run and can make it to an Apple store, this would certainly be a good chance to check it out!
Source: The Tonight Show Starring Jimmy Fallon