Oh N also makes an appearance in Anville Town in B/W2. A girl loses her Pansage in Anville Town, so you go look for it around Nmbassa City. There will be a green man with Pansage, and they will head to Anville Town. When the girl is reunited with her Pansage, she'll say this:
'Oh silly Pansage. A man with GREEN hair said that Pansage's DREAM was to be a railway conductor'
Who do we know that has Green hair and can talk to Pokemon....?