A/N: I'm called "Spontaneous Fiction" for a reason you know. And here I am with another novelty and befuddlement. I'm disappointed in all of you for not making this crossover sooner. Like, really guys we were gifted an allusion to this in the 2nd episode of season 1 and NO ONE thought to try it out? Oh well. Without further ado, I bid you adieu.

Disclaimer: It is common knowledge that I do not possess the right towards Gravity Falls. I do however possess a Stan fez. Oh, and I don't claim ownership to anything created by George Lucas or Steven Spielberg. The franchise of Indiana Jones belongs solely to them, as well as their abandoned scripts and their used ones.

Prologue: What's Old, Shiny, and Belongs in a Museum?

1912

The hot blistering heat of the California shone down on the group of riders on horseback. They followed the beaten path of a trail, one created many years before their arrival. Their horses plodded steadily on, at times tossing their heads for no reason other than to probably look pretty. They're horses. Who knows what they were really doing. They certainly didn't ask to be in the heat on a day like this.

The leader of the group pulled his mount to a stop and the others behind him followed suit.

"Dis-mount!" he called out. The group of teenaged Boy Scouts collectively swung their legs over the saddles, dismounting from each of their rides. They all looked around their environment, some more eagerly than others. Their troop leader had stopped them by the side of the mountain. Many of the boys quickly discovered that the mountainside was riddled with holes and caves. The adventurous Scouts were fully prepared to investigate all of them and set out to look at a few.

"Alright boys, don't anybody wander off!" Their Scoutmaster called out. "Some of these caves can run for miles and I don't want to fill out any paperwork if any o' you got lost in them." His words went ignored by the teens, as words said by adults generally are. Teens these days.

Two of the scouts were already well into one of the cavern tunnels. At first they thought it wouldn't have led them far. But as they kept wandering into the depths of the mountain they discovered that it was deeper and further than they originally thought. The air grew colder and the floor wetter as they kept walking.

"Maybe we should head back," one of them said. He was anxiously looking over his shoulder, back in the direction they came.

"Wait, did you hear something," the other whispered.

"No! Look let's go back before Mr. Corduroy gets-"

"Shut up!" The boy in front grabbed his friend's arm, pulling him forward much to the other boy's protests. After a few more meters they did hear something. Voices. They echoed down the tunnel in front of them almost eerily. The two edged up the cave tunnel cautiously. Ahead of them was what appeared to be candle light, most likely from a lantern.

"I've got something!" a voice shouted from ahead. The boys peeked their heads around the corner of a connecting tunnel where the light source originated from. There were four men in the adjacent cavern. Three of them showed signs that they had previously been digging. Dirt and clay covered their faces and parts of their clothing. Only the fourth man, in a fedora hat and brown leather jacket, had no traces of dirt on him. One of the diggers was busily trying to open an old wooden chest, finally jabbing his spade at the lock which successfully shattered, leaving the chest to be opened. The man in leather (obviously the leader) stepped forward to open the chest. He began pulling things out of the chest, carelessly dropping them on the cave floor until he paused and slowly pulled out an object from the bottom. The light of the lanterns reflected off of the object and smaller dots of light danced on the walls. The fedora man turned slightly and the boys' eyes widened in shock.

Held in the man's hands was an ornate golden and bejeweled cross. They held back their gasps as the other robbers began cheering, shouting, "We're rich! Woohoo!" and similar exclamations.

"What are they doing? Hey Dip. Dipper? Dipper?" The scout Dipper ignored his friend, intently studying the golden cross in the man's hand. After a while he began to recognize it and grit his teeth in anger.

"That's the Cross of Coronado. Given to him in 1521. That artifact belongs in a museum," he hissed quietly. His friend said nothing, only giving him a worried look. Dipper's mind began to race. They had to get that cross away from these thieves and to the sheriff. He turned back to his fellow scout.

"Go back to the others. Find Mister Corduroy and tell him there are men looting the caves. Have him bring the sheriff." He whispered. The other boy blinked and nodded.

"What are you gonna do Dip?" he asked. Dipper glanced back around the corner to the four men. Apparently they found more artifacts because the three began intently digging again, the leather man urging them on. The cross was placed on top of their other equipment on the other side of the cavern. Dipper shrugged at his friend.

"I'll make it up as I go along."

Dipper had never done many "sneaky" things in the past. Once or twice he'd tried sneaking past his Grandpa and Great Uncle to get out of the house. Unfortunately in one of the two adults' spare time they taught their pet how to guard the house, resulting in the teen getting caught on both attempts. But this time there was no guard, and the men were all too focused on their digging to pay any attention to the boy as he crept into the cavern. He made sure his footsteps were light, barely making a sound against the wet floor. Keeping an eye on the looters, Dipper reached out and grasped the golden cross tightly in his hands. He held his breath as one of the men straightened up, but he was only stretching his back and went back to work, the man in leather barking more orders at them.

"Dig with your hands damn it, not your mouth!" He said. Dipper put the cross carefully in his back pocket. His heart pounded like crazy in his chest. Was he actually going to get away like this? Mind focused completely on the looters, he failed to notice the duffel bag of equipment in front of his feet. He stumbled forward, arms spinning to regain his balance and knocking a nearby lantern to the ground. It shattered and extinguished the light, causing the four men to shout in surprise at the sudden loss of lighting.

Dipper picked himself up and scrambled out of the small cavern, making a run for the tunnel. The man with the fedora shouted again, his angry words echoing against the walls and following Dipper out of the mountain.

"Get your heads out of those holes and get that thief!"

Shoes slapping against the floor of the tunnel, Dipper ran and ran fast. Just as he thought his heart or lungs would explode he shot out of the cave and into the open air. Glancing around, he suddenly noticed no one was around.

"Mister Corduroy! Alex? Anybody?" He began calling out. No one answered him. The teen groaned in frustration.

"Everybody's lost but me," he murmured. The shouts from the caves got louder and Dipper spun around in panic. The men were going to gain on him. He stuck four fingers in his mouth and blew, creating a shrill and short whistle. A whinny came from the trail and his horse quickly trotted over to him. Wasting no time, Dipper swung himself onto the mount, snapping the reigns as soon as he was in the saddle. The auburn horse took off at a gallop and raced away from the cave just as the men came flooding out of it. One of them took aim with their pistol and fired off at Dipper, but it was no use and the boy was already gone in a cloud of dust riding as hard as he could back to town, the Cross of Coronado stashed in his back pocket. The man in the fedora and leather jacket shouted at his fellow looters, ordering them to get their trucks to chase after the kid. As they did he watched the quickly receding dust cloud of horse and rider. And he gave a small smile.

Dipper didn't really know what he was going to do with his horse. He had only planned as far ahead as getting out of the cave alive and unnoticed though so far he'd only gotten the alive part down. He galloped into town avoiding automobiles and angry pedestrians, intent on making it to his house. Soon he pulled his horse to a stop outside a run down two story house. There was barely anything to the lawn except for a lone tree and a mailbox in the front of the house, the name "Pines" painted in light blue on the box. Dipper hurriedly dismounted again, his frantic actions almost causing him to fall off instead, and tied the animal up on the tree in the front yard. He then sprinted to the front door, swinging it open and dashing to his grandfather's study.

"Grandpa Stan!" He shouted. The man was generally always in the study, working on some thing or other like translation of old documents. As he rounded the corner to the hall he crashed into something, sending him backwards and to the floor.

"Hey watch where you're going Bro." Across from him on the ground was his twin sister Mabel. Even in the midsummer California heat, she still insisted on wearing a bright sweater. Dipper helped her up muttering a quick "sorry" before heading back to his grandfather's study.

"Where's the fire?" Mabel called after him.

"Tell you later!" Her brother replied. Mabel sighed and went her separate way, then gasped as she saw what was standing in her yard by the tree.

"Oh my gosh a horse!" She squealed in delight and ran outside immediately. Meanwhile Dipper quickly opened the door to the study, excitement bubbling in his chest as he prepared to show his Grandpa what he'd found.

"Grandpa Stan," he started.

"Out,"

"But Gramps, you won't believe-"

"If its that important, count to twenty," the man said. His back was turned to Dipper, hunched over his desk. Papers and books were scattered across it. Dipper contained his frustration and began to count to twenty. It was an exercise the family had come up with when they had "important" things to say. If you still needed to talk about it after making it to twenty slowly, then it was deemed so. But his Grandpa stopped him by holding up a finger.

"Do it in Latin," he said.

"Unus, duo, tres, quattuor," he began reciting, the excitement from earlier quickly dissipating. His eyes wandered to the window which showed a view of the street. As he slowly kept counting, the sheriff's car suddenly pulled into view. In the backseat sat his friend Alex, who look incredibly proud of himself. Dipper slowly began retreating from the room, still counting in Latin but it didn't seem as though his grandfather was noticing anything he was doing. With a last look at the hunched and working figure, the teen left. Stanley Pines made a few more etches with his fountain pen onto the page.

"Three trials. Illustratio," the man muttered under his breath. The image of an Eye of Providence stared back at him from the page, leaving his questions unanswered.

Outside the house Alex ran up to meet Dipper, pointing excitedly at the car.

"I did it! I got the sheriff," he exclaimed. Said Sheriff by the name of Blubbs exited his vehicle, coming up to the two boys.

"Now as I understand it you found something in the caves?" the man asked. Dipper and Alex nodded.

"You have it then?" Dipper extracted Coronado's Cross from his back pocket, handing it to the sheriff. The older man took it, and turned around back to his black vehicle. Failing to notice it before, Dipper now saw that there were two passengers in the car as well. One of them was a big pudgy man in a white suit and straw hat, and the other was-

"You!" Dipper gasped. The man in the fedora hat grinned at him, tipping his hat. Sheriff Blubbs handed the cross to the man in the suit who looked very pleased to have the object in his possession.

"I hope you won't press charges against the boy," Sheriff Blubbs was saying to the man.

"No of course not. Everything's in order now and the artifact is safe. My business in this town is done," he replied, eyes wandering hungrily over the cross. The sight of it made Dipper sick. He had been so close! If only that man hadn't bribed the sheriff, the cross would have been safe in the hands of a museum. Now it wasn't, and there was nothing he could do about it.

"Hold on a minute boss," the car door opened and the fedora man stepped out, walking towards Dipper. He glared at the man, who smiled ruefully.

"Look, you lost today kid. But that doesn't mean you have to like it," he said. Then with a second thought, he took off his prized hat, plopping it on top of Dipper's messy brown hair. He turned, gave a backhanded wave and made his way back to the sheriff's car.

"See you around kid," he called out. Dipper adjusted the fedora on his head as the car pulled away, the teen watching it go. He swore, right then at that moment, in front of his grandfather's and great uncle's house with its shabby painted mailbox and horse tied to the tree, that he'd get that cross back. It belonged in a museum. And Dipper Pines would be damned that he'd be the one to put it in one.

A/N: PHEW. Oh my stars that was a bunch to write. What is this, like 2,000 words? Yep. After this I can get to "normal" sized chapters. I just really wanted this prologue to be one chapter though, seeing as its the intro. Basically this will be a re-write of "Indiana Jones and the Last Crusade" but of course with Gravity Falls characters instead. I've also taken the liberty of changing scenes around to best fit the characters and the original stories from both mediums. Please send a review my way if you like what you see, or have things to point out to me. I'm only human after all, and make tons of mistakes. This is Sponty, signing off 'till next time!