End of Demo Code

Upon beating the demo and getting all 10 canisters you recieve a code for use in the normal game. Also listed in the pause menu once you unlock the three unlockable characters are codes that correspond to each, presumably for unlocking them in the normal game.
Password                Effect
NAH118                  Unlocked by finding all 10 canisters
PEJ821                  Unlocked by unlocking Greedo
JAW499                  Unlocked by unlocking the Jawa
YDV451                  Unlocked by unlocking the Sandtrooper


Easter Eggs
Play as secret characters in the demo version

First of all, complete the demo, which will unlock the "Free Play" mode.
Then, enter that mode and you'll be able to create 2 characters. Continue playing and you'll see only the two of them in the map. Press the key to switch characters, and depending on the area you're currently in, different characters will appear. You can not only play with most characters from the demo, but also with the Emperor, from Episode VI.