Pinescone is the crossover shipping of Dipper Pines and Wirt from Over the Garden Wall. It has a very significant presence in the fandom, and is a remarkably popular ship despite being a crossover.
Dipper and Wirt are incredibly similar characters; they're both paranoid, perceptive, pessimistic, adorable, awkward, anxious, dorky, enjoy reading, have low self-esteem, have had encounters with the strange and supernatural, have bouts of selfishness, and still have a silly/childish side to them. Thus, the two are believed to get along extraordinarily well if they existed in the same universe, and are depicted sharing stories, exploring/adventuring together, and becoming close friends since they both understand each other and how one another thinks/feels. They are commonly portrayed eventually pursuing a higher relationship, but not after hiding their feelings and awkwardly confessing.