This gentleman, are for you, that wont play the whole Episode 6 and all that boring stuff.
How to Unlock Darth Vader
I don’t know how many gold bricks you’ll need for this, but it’s not much. UPD: 20 Gold Bricks!
First of all you have to complete the first ep of Episode 4 a new hope, then if you have enough gold bricks, you can play the extra level at Mos Eisley Cantina (Episode 4) just finish the level and you will be awarded with Darth Vader and a Stormtrooper.