Do the quest that involves retrieving a strange idol which frightens the local townsfolk. There are three screens of scrubby desert that Indy must walk through before reaching the temple with the idol. Wait around in these screens for awhile by taking the time to kill all animals present instead of immediately going to the temple. When you finally continue, instead of locating the temple with C-3PO's head, you will find a boat. Use it to cross a lake. Next, find the "Y" shaped rut in the ground with three stone blocks. Move the blocks to the endpoints of the "Y" shaped marking. Indy will be kidnapped by an alien, who mentions that you have too much time on your hands. The quest ends with the spaceship leaving Earth.
Star Wars reference
One of the main quests involves retrieving a strange idol which frightens the local townsfolk. When Indy enters a hidden temple and finds the idol in question, it turns out to be C-3PO's head.