Have you ever noticed the Alien on the 4th island? He crash-landed and ended up in this dimension too.
Your job is to help him. It's rather rewarding; You get charm, some Solar Matter (needed for the Nova flamethrower) and even a trophy.
The first time you talk to him, he will ask if you've got a spare Hyperdrive. If you've got it, give it to him. If not, fight in the The Brand New Abandoned Warehouse to get it.
He'll be very happy when you give it to him. The next part is to give him Nanobots.
In order to get the Nanobots, you need a card to get into the Benjamin Club ($50,000 or $25,000 with cheats) AND you need to buy the Nanobots from the dealer who hangs in there ($45,500 or $22,750 with cheats). He is found from the afternoon till late. It is very expensive, but it is rewarding.
Give it to him and in return you will get your rewards stated above.