Twitter has been translated in quite a few languages so far. More recently, it's been relying on volunteers to provide translations for countries all over the world. The latest language added to Twitter doesn't really have a country though, not unless you count the internet as one.
Twitter has added a LOLCATZ language option, making it possible for you to experience Twitter in the universal language of the internet.
"Happeh Fridai! U can nao change ur language 2 lolcat in Settings. Hope u liek it," the official announcement
You can switch right away by visiting twitter.com/?lang=lolc, or you can go to the Twitter Settings page and change the language.
Fair warning, the language is still considered in beta, so there may be a few problems and mission phrases here and there.