The 31-year-old rapper took to Instagram to share a video in the studio with the 'Personal Jesus’ rocker.
In the clip, the shock rocker could be seen singing into the microphone “crazy like Marilyn Manson”.
Ferg captioned the post: "Running it up @marilynmanson."
He also shared a selfie of the pair on the photo-sharing app.
The hip-hop star's latest track was the freestyle, ‘Feel Some Type Of Way', released in May.
As for Manson, he's been teasing fans about his upcoming 11th studio album.
Last week, he simply wrote on social media: "Prepare."
The record is the follow-up to 2017's 'Heaven Upside Down' and Manson recently revealed it's complete.
Last April, the 51-year-old singer teased that the record has a "different vibe" after he worked with country star Shooter Jennings again.
Manson - who teamed up Jennings on a cover of David Bowie's 'Cat People' in 2016 - said: "I felt like it was a good time for a change, and I became friends with Shooter.
"And he's a musical genius. Shooter, he kind of reminds me of The Dude from 'The Big Lebowski' ... "But we have this different vibe where I don't have to really tell him what I'm thinking.
"I didn't know this, but he was a fan of what I did growing up, also underneath his father, Waylon Jennings. So he adds a completely different element."
Meanwhile, 2019 saw a new drummer, Ho99o9's (Horror) Brandon Pertzborn, join Manson's band.
Gil Sharone - who featured on his 2015 album 'The Pale Emperor' and 'Heaven Upside Down' - announced his departure after five years playing together to "pursue other projects" last March.
And, three months later, the 'mOBSCENE' rocker introduced his replacement.
Alongside a black and white picture of the pair, who bonded at the cinema, Manson wrote on Instagram: "I went to see a film with @strainsofhorror Shayne and my drummer Brandon. @brandonpertzborn (sic)”