Anthony Mackie Warns David Harbour About Working With Sebastian Stan (Exclusive)

'Just give him some almond butter.'

David Harbour is a relative newcomer to the MCU -- he debuted his role as Alexei Shostakov/Red Guardian in 2021's Black Widow and is set to reprise the character in the upcoming Thunderbolts team-up. 

So when it came time to learn everything he could about his future castmates, he turned to We Have a Ghost co-star Anthony Mackie, who had some particular advice about his franchise frenemy, Sebastian Stan, who will also be appearing in Thunderbolts as Bucky Barnes, aka The Winter Soldier.  

"Sebastian is a very nice person," Mackie said with a grin as he and co-star Jahi Di'Allo Winston spoke with ET's Ash Crossan this week.

"Don't take his quietness and standoffishness as him being mean or rude. You just have to warm him up a little bit," he teased. "You know, give him some almond butter, talk to him a little bit. He'll be fine."

Thunderbolts is still in early development, with production rumored to begin this summer. In addition to Stan and Harbour, the team-up will bring together a cast of misfits from across the MCU -- including Florence Pugh as Yelena Belova, Julia Louis-Dreyfus as Contessa Valentina Allegra de Fontaine, Wyatt Russell as John Walker/U.S. Agent, Hannah John-Kamen as Ava Starr/Ghost and Olga Kurylenko as Antonia Dreykov/Taskmaster. 

Mackie will next appear in the MCU as Sam Wilson, aka the new Captain America, in Captain America: New World Order, due out May 3, 2024.

But first he's got some spooky spectres to deal with in Netflix's We Have a Ghost, a family-friendly horror-comedy from writer-director Christopher Landon, based on the 2017 short story "Ernest." The movie centers on a family that goes viral online after recording footage of Ernest, the mute but mostly affable ghost living in their attic.

When the co-stars were asked how they would behave if they became ghosts for a day, Mackie was slightly offended when Winston said he would choose to haunt him.

"There's so many people you could haunt!" he replied, adding with a laugh. "I would haunt my high school girlfriend."

ET also spoke with Harbour about filming in New Orleans with the Big Easy native. The actor said he had a blast, laughing that Mackie "really is the mayor."

"We went out a couple of nights," he shared. "I don't drink -- I haven't drank for like 20 billion years or something. But I do like to smoke a cigar every now and again. So he took me to a great, really trashy dive cigar bar, downtown... He really does know everybody in the town, so it was pretty fun to hang out with the mayor."

We Have a Ghost premieres Feb. 24 on Netflix.