Version-exclusive Pokémon in Black 2 & White 2
Like all the paired games in the Pokémon series, Black 2 & White 2 each include Pokémon that cannot be obtained in the alternate version. To obtain Pokémon missing from your version you need to trade with someone who has the opposite version.
Due to the Unova Pokédex being expanded in Black/White 2, there are a few more exclusive Pokémon here. Note that a few Pokémon listed here are available via other methods: Cottonee/Petilil are available via an in-game trade, and Regice/Registeel can be obtained using the Unova Link feature.