Now there are calls by anti-bullying campaigners to ban the app in the UK too.
The app, called SimSimi, can be "taught" responses by any user when certain names or words are typed in.
It means that users - many of whom are school pupils - are getting abusive replies when they type their own names in to the app.
"I think they have a duty of care of suspend the service for all young people," says Liam Hackett of anti-bullying campaign Ditch the Label.
"Their content is predominantly negative, abusive, sexually graphic or violent."