Dipper had just returned to Gravity Falls after five years he was thirteen the last time he set foot in the place and now he's an adult. It's something that he's still processing and coming to terms with. He has grown a lot since then and is taller than he used to be. His dorky nature hadn't changed at all.
He decided to walk around the forest to clear his mind. Mason debated what to do first, talk to Pacifica, ask her out, or check up on Soos and see how he's doing. The options were there however it remained to be determined what he'd go ultimately with. After, he was roaming around for at least a half hour. He decided to head to the Mystery Shack memories were running rampant in his mind.
He entered the building and took a look at his surroundings it looked different, granted, weird crap was still in there, but there were also new decorations. It seemed to be remodeled in five years. He sat down on a bench once he had done so, he saw you enter the store. Dipper didn't pay much attention until you tapped his shoulder, turned around, and looked at you. "Hey there. I'm Dipper you need something?" He asked you.