Kazumi Totaka is one of Nintendo's most experienced and talented composers and sound directors, yet that's probably not the reason that many recognise his name. He's better know for Totaka's Song, a simple melody that has been hidden within a whole load of Nintendo games. The first appearance seems to have been in X on Game Boy, though the first example that was widely known was in Mario Paint.
The basic song has become a favourite among dedicated fans, and finding it is a great part of the appeal; if Totaka-san has worked on a game the search is guaranteed, but the occasional curve ball means that it can take quite a while to stumble across it.
YouTube channel Somewhat Awesome Games claims to have found it in Mario Kart 8, sung by a Yoshi (Totaka-san is the voice actor for the character) on multiple tracks. The example below is in Yoshi Valley, with the song being very faint until isolated in the audio.
It's a pretty cool discovery, and if you don't know what the heck Totaka's Song is, the compilation video below should help.