Up sprung is a phrase that means "suddenly appeared." There are a variety of synonyms for this phrase that can be used to add variety and nuance to your writing. Some possible options include "emerged," "arose," "burst forth," "popped up," "appeared suddenly," and "suddenly materialized." Depending on the context and tone of your writing, different synonyms may be more appropriate. For example, "arose" may be a more formal or poetic choice, while "popped up" might be a more casual and playful option. Experiment with different synonyms to find the one that best fits your writing style and the message you want to convey.