In the 'Ash Gets a Pokemon Egg' fanfiction, it might be a local villager. The villager could have found the egg in a nearby forest and, knowing Ash's reputation as a Pokemon trainer, decides to give it to him. Or perhaps it's a scientist who has been studying the egg but realizes that it belongs in the hands of a trainer like Ash, where it can grow and thrive in the wild rather than in a laboratory environment.
Maybe it's a legendary Pokemon in disguise. In some fanfictions, legendary Pokemon often play important roles. It could give Ash the egg as a test or because it senses that Ash has a pure heart. Another possibility is that it could be a young trainer who can't take care of the egg anymore and trusts Ash to do a good job.
He might meet an old Pokémon expert who gives him tips on hatching the egg.
Team Rocket would be the most obvious ones. They're always after rare and powerful Pokémon or Pokémon - related items, so the legendary egg would be a huge target for them.
It could be a legendary Pokémon in disguise. Legendary Pokémon sometimes interact with trainers in mysterious ways. This one could have chosen Ash to receive the Dratini egg as part of some grand plan to help Ash become an even greater trainer and perhaps save the Pokémon world from a future threat.
In this fanfiction, Ash might take really good care of the Pokemon egg. He would probably keep it warm and safe, waiting eagerly for it to hatch. Maybe he'd even talk to the egg, like he does with his other Pokemon friends.
It could be an Eevee. Eevee is a very common yet special Pokemon. It has the potential to evolve into many different forms, so it would be an interesting addition to Fem Ash's team.
His friends like Pikachu for sure. Pikachu would be there by Ash's side, probably as curious as Ash about the Dratini egg. Brock might also be involved. He could use his knowledge of Pokémon to give Ash some tips on taking care of the egg.
In this fanfiction, Ash could face a lot of challenges while taking care of the Pokémon egg. There might be other trainers or Pokémon who try to steal the egg. He would have to protect it at all costs. Also, he could meet some new friends who help him with the egg. They might give him advice on how to keep the egg warm and safe. And when the Pokémon finally hatches, it could form a really strong bond with Ash right from the start.
Perhaps an ancient evil spirit that was sealed away long ago. The hatching of the legendary starter's egg is a sign that the spirit can break free. It wants to possess the starter to regain its full power and take over the Pokemon world. This would make for a very dark and menacing antagonist, and Ash would have to use all his skills and the power of his friendship to defeat it.
Well, in this kind of fanfiction, Ash might take really good care of the egg. He could keep it warm and protected all the time. Maybe he'd build a special nest for it. And when it hatches, it could be a super powerful legendary Pokémon that immediately bonds with Ash and helps him in his Pokémon journey.
His friends like Misty and Brock would probably visit him.