Once you have gotten all of the Spindex games you will be awarded with a secret souvenir that you can only get once you have completed the Spindex.
Submitted by Sarah D. The Game Genious
When in certain menus, if you turn the GBA back and forth rapidly, and listen really hard, you will notice that the music slows down. Here are the menus that I know will do this:
All Spindex Menus (except Main)
See if you can find somewhere else to do this...
Submitted by puregenius12