Here's what would happen: Team Rocket would attack the kids AGAIN, and manage to snag all of their Pokemon except Pikachu. Then the machine they use malfunctions, and everybody's Pokemon (Ash, May, Brock, Jessie, and James, including Meowth) are blown away quite a distance. While the Trainers are hospitalized, Pikachu tracks down its missing friends. Eventually, he winds up in Central Town, where we can understand all the Pokemon as if they were people. Pikachu finds May's Squirtle and James's Mime Jr and form a Rescue Force called "Star Squad" (because their friends fell here like shooting stars). For the next 13 episodes, Pikachu plays the lead role in the Rescue Force games and takes on missions that help him find their friends. Over the course of the series, though, they run into fierce rivals (like Seviper, Cacnea, and Dustox), new friends (Charmander, Abra, and Larvitar), unusual allies (Meowth helping Pikachu?!? What's he up to?), and even 4th Generation Pokemon (an evil Weavile, noble Rukario, maybe even cute, li'l Manafi). It also ties in elements of the MD games, like Heroes + Absol vs. Articuno.
This is Pikachu's Mission: Mysterious Dungeon.