I recently bought White 2 used, and the previous owner had made it to the Elite Four. Other than the starter, are there any Pokemon they might have chosen over another (and so I should attempt to trade that to another player and then trade back once I start anew)? A similar scenario would be the Mount Moon fossils in Red and Blue; one can only get both in the same playthrough via trading with another player.
Pokemon Black 2 White 2 – Are There One-Time Pokemon to Choose Between in White 2?
pokemon-black-2-white-2
Best Answer
Your starter and your Fossil Pokémon
As you mentioned, and like most other games in the Pokémon franchise, you only receive one of the three starter Pokémon in a playthrough without trading, which is selected at the beginning of the game.
Generation 5 also has a pair of fossils, of which you can only select one during a particular playthrough of the game. Selecting the Cover Fossil will get you Tirtouga, while the Plume Fossil will get you Archen. In Black/White 2, you receive your fossil from Lenora in the Nacrene Museum, while in the original Black/White, you receive your fossil from a Backpacker in the Relic Castle.
Both versions of the game also have a set of version-exclusive Pokémon, but which of these you have access to is, of course, determined by which version of the game you have, rather than choices you make during the game.