Erin is a bastard means that Erin Noble is basically a bastard! She loves the word as she was the one to create it!! She classifys that as her ‘special’ word, and it’s true it’s her favourite word and no one else should use it!

Phrase used usually to describe someone who is a Genius and a Son of a Bitch at the same time, or in other occasions, someone who, even being a total idiot, is someone that you admire in some way

In some rare occasions, it's also used when you want to say good luck to your Best Friend in an Humorous way
it has it's origins on a Greentext from an user on 4Chan where the user describes himself playing a game with another person

you fokking bastard is what you say to a fokking twat who is fokking sthcewpid