Baby, you can drive my car...
This one's fun, and useful too. Go into 'Secret Plans' in freeplay. You need to have, at least, a jedi and a stormtrooper. Access the stormtrooper-only areas. In a back room, there are stalls with big shower heads over them. Use the Force to activate the individual showers. Flowers and plants will grow. Mow them down with your lightsaber for lots of studs. In the first row on the right there's a red brick. In the row on the back wall, you'll get parts to build a little car. Hop in, and drive about the ship (more fun than walking!) Eventually you'll come to the crane room. Drive (carefully) onto the floor jack. It will raise up and you can get a minikit.
We have more cheats and tips for this game here, LEGO Star Wars II: The Original Trilogy cheats
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