Super Game Boy Easter Eggs

Start a game and select a border from the menu (press L+R). Press L 4 times, R once, L 4 times, and R once. A screen saver will start playing. (With the movie theater border, you can see kids playing Game Boy.)

Insert the Super Game Boy system into your Super Nintendo (SNES) and insert any Game Boy game.
Turn on the power and wait until the game actually starts to show.
Quickly (with no more than about a half second pause between buttons) press LLLRRRLLLRRRRRRR... more