Perhaps they are just having a relaxing time. They could sit under a tree and talk about their future plans. Tails might be thinking about building a new base in the woods, and Sonic could be excited to have a new place to start adventures from. They could also be looking for a special type of flower or plant that only grows in that part of the woods for some important reason in the fanfiction.
They might go on an adventure. Maybe they'll discover a hidden treasure or face a new enemy together.
In the fanfiction, when Sonic meets Tails in the snow, they could also just have a friendly chat. They might talk about their past adventures, like the time they saved the world from Dr. Eggman. Tails could share some new inventions he's been working on, and Sonic would be excited to hear about them. They might also plan their next adventure while enjoying the snowy scenery.
In a fanfiction where Tails meets Sonic for the first time, Tails might be in awe. Sonic's speed and heroic reputation could make Tails instantly idolize him. Maybe Sonic saves Tails from a dangerous situation, like a group of badniks. Tails, being the smart fox he is, could then offer to help Sonic with his gadgets, starting a great friendship.
One possible plot is that Sonic is exploring a new area. He comes across a small workshop where Tails is building his first plane. Sonic is intrigued by the little fox and his inventions. Tails is initially startled by Sonic's sudden appearance but then gets excited to meet his idol. They start chatting about their adventures, with Sonic sharing his tales of running fast and Tails talking about his love for inventing things.
In this fanfiction, perhaps Sonic Underground is facing a threat that they can't handle alone. Tails, being a friend of Sonic from another part of their world, comes to their aid. They discover that an ancient evil has been awakened. The story could involve Tails using his inventions to analyze the ancient evil's weaknesses while Sonic and his siblings use their unique abilities to keep the evil at bay. As they progress, they form a strong bond and learn from each other's ways of doing things.
In such a fanfiction, they might start by being a bit skeptical of each other. Modern Sonic is used to his high - speed, action - packed world, while Boom Sonic has his own unique charm and way of doing things. They could end up in a race to prove who's faster, which would be really exciting to read about.
Well, they could have an epic race. Modern Sonic is all about speed and his cool modern moves, while Classic Sonic has his own charm. They might start competing, with each trying to outdo the other in different terrains. It would be a showdown of different Sonic eras.
In a 'sonic meets pokemon fanfiction', Sonic could end up in the Pokemon world and start racing against some of the faster Pokemon like Rapidash. Maybe he'd form an unlikely friendship with Pikachu, with Pikachu using its electric attacks to help Sonic out of tough situations, like zapping robotic enemies that Sonic might encounter in this new world.
Maybe they received some sort of signal or message that led them to the woods. It could be a distress call from another character or a sign of something important. Another possibility is that they planned to meet there. Tails could have found something interesting in the woods and asked Sonic to come see it. Or Sonic might have suggested the woods as a meeting place to discuss some private matters away from the hustle and bustle of their usual places.
In a Sonic meets Captain Marvel fanfiction, there could be a plot where Sonic's rings have some sort of connection to the power of the Tesseract (which is related to Captain Marvel's story). They both have to figure out what this connection is and how to use it to save both their worlds. It could be a really exciting adventure with Sonic zipping around and Captain Marvel blasting enemies with her photon blasts.
Well, Sonic might have some exciting adventures with his siblings. They could team up to fight against a common enemy, like Dr. Eggman. It would be really cool to see how they use their unique abilities together.