One possible love story in Gravity Falls could involve Mabel and a local boy. Mabel is this bubbly, creative girl. She might meet a boy who shares her love for arts and crafts. They could bond over making sweaters or creating some unique art pieces inspired by the strange creatures in Gravity Falls. They start spending more and more time together, going to the town fairs, and sharing their dreams. Their love story could be about two kind - hearted souls finding each other in this weird and wonderful town.
There could be a love story between two of the mystery - solving side characters. Maybe a couple of the guys who work at the local store that's always full of strange artifacts. They start to realize they have feelings for each other while researching about some of the more dangerous items in the store. Their love story would be filled with moments of danger as they deal with the supernatural elements associated with the items, but also with sweet, quiet moments when they're just looking at each other across the store, knowing that they have something special.