The phrase "pops up" often refers to something suddenly appearing or becoming visible. There are several synonyms that can be used in place of "pops up," such as materializes, emerges, surfaces, springs up, and appears unexpectedly. These words convey similar meanings, but each may have a slightly different connotation. For instance, "materializes" suggests that something previously unseen becomes tangible or concrete, while "emerges" implies a gradual or deliberate manifestation. "Surfaces" suggests something has been hidden or buried, while "springs up" suggests a sudden burst of activity. Using these synonyms can add variety and depth to your writing, while expressing a specific nuance of meaning.