Peter's longtime collaborator Mark Wahlberg personally suggested they recruit the "Rockstar" hitmaker to join the line-up for their upcoming crime drama, but the filmmaker began to worry about Malone's lack of acting experience when the 23 year old showed up for his first day on set.
Wahlberg, who also serves as a producer on the project, admits they took a chance on Malone because neither of them had met the hip-hop star prior to offering him the part of a prisoner without having him audition.
"I just said I want him in this part, which is a pretty big role in the film, and Post showed up (to the set) and Pete was like, a little nervous, because (Post) was drinking Bud Light (beer) fairly early in the morning!" Mark smiled on U.S. daytime show "The Talk".
"He's a rock star, but all of a sudden, (Berg) was like, 'OK, let's rehearse the scene,' and Post wouldn't do it for real, he was just kinda mumbling through the words."
Luckily, when the cameras actually started rolling, Malone, real name Austin Richard Post, proved his worth and really impressed Mark and Peter, who ended up reworking the screenplay to give the rapper a beefier part.
"He eventually knew the words, but when he came on set (to shoot), it was like magic," Mark recalled. "The scene is brilliant, and he's now coming back, he's got like, three or four other scenes.
"We basically combined what were two roles into one role, just because he's got so much talent."
Wonderland is based on Ace Atkins' 2013 novel of the same name, which follows a detective as he uncovers the truth about a sensational murder and the twisted conspiracy behind it, and Wahlberg reveals Malone's multiple tattoos helped him settle right into his role.
"Do you think he's believable as a convict in a state prison with those tattoos on his face?" he smirked.
"Wonderland", which also stars Black Panther's Winston Duke and veteran actor Alan Arkin, is currently in production and is set to be streamed on Netflix, although it has yet to be given an official release date.