Robert, who wanted to be a rapper when he was younger, has the music to thank for his authentic American accent.
He also revealed that co-star Kristen Stewart is sometimes unimpressed with his efforts.
Speaking to Oprah Winfrey, Rob said: “I used to want to be a rapper when I was like 14, I swear to God!”
“I have a lot of recordings, I used to do an American accent.”
“Kristen thinks I do the most terrible accent,” to which Kristen replied: “No, I don’t, just occasionally something little will come out and I’ll say ‘We don’t do that!’”.