Executive Meddling: Several songs were purportedly chosen because Nintendo of America president Reggie Fils-Aime liked them. In addition, many rumors of a sequel exist purely based on the fact that Reggie was apparently quite fond of the game. Not that him getting us a sequel would be a bad thing.
In fact, it seems that September and a Jamiroquai track have to be in every music game Nintendo has some hand in, being as they are in EBA, Donkey Konga and... well, that's it.
September and Material Girl are also in Wii Music.
Hey, It's That Guy!: A few characters from Ouendan appear in this game, especially noticeable with the lead actor in Romancing Meowzilla, who previously appeared as a character in the second stage in Ouendan.
Hey, It's That Voice!: The covers of Walkie Talkie Man and Canned Heat are sung by Jason Paige, best known for his first-season Pokémon theme.
The cover of "SK8R Boi" was apparently sung by the same person as the theme song for Kim Possible.