Bulbapedia says that, because of some oversight, they sometimes behave like Japanese Pokemon. Does this include the Masuda Method? Please don't question my curiosity. Kazza, Charap, and Gaspar are the Abra, Chatot, and Haunter that in-game NPCs trade to you.
Happily, these three Pokemon are effective for Masuda breeding in Diamond and Pearl --- but only in an English copy.
In the English language version of Pokémon Diamond and Pearl, Kazza, Charap, and Gaspar are functionally Japanese in origin; in Pokémon Platinum and all other language versions of Pokémon Diamond and Pearl, these Pokémon have the same language of origin as the game they were obtained in. While language of origin is normally not visible in Pokémon Diamond and Pearl, being a different language of origin does still have functional effects, such as boosting their experience gained by 1.7× (instead of 1.5×) and being applicable for the Masuda method.
Generation IV in-game trades (Bulbapedia)