Not sure if this has been discussed (or if anyone even cares) but in the DSi sound application, if you select a recorded sound and let it sit for a while, it'll start to play a Mario song with the sound you recorded there.
Hard to describe.
http://www.youtube.com/watch?v=PUePmQ3c_jI
Hard to describe.
http://www.youtube.com/watch?v=PUePmQ3c_jI