Nicki Minaj has a surprise in store for her Barbz. With little over a month to go until the release of her sophomore album Pink Friday: Roman Reloaded, the rap diva hinted at a big collaboration.

“Just got some heron from one of ur fave artists. In the studio shakin my fuckin head right now. WOW. Roman Reloaded,” wrote Nicki during a late-night tweet. “Like. Yall will fcn spazz.”

She remained tight-lipped, but dropped one clue about the mystery feature. “Never worked w/’them’ b4,” she told one of her fans.

The follow-up to the Young Money rapper’s multi-platinum debut Pink Friday, due on Valentine’s Day, has spawned the singles “Roman in Moscow” and “Stupid Hoe,” for which videos have been shot.

Who do you think is the surprise guest? Share your thoughts below.