Luigi Mangione’s job in federal lockup is cleaning showers — and he’s a one-man welcoming committee, according to a fellow jailbird. 

Upon his arrival at the Brooklyn Metropolitan Detention Center in Sunset Park, Michael Daddea was informed by a guard that he would be staying in the same unit as the individual accused of assassinating UnitedHealthcare CEO Brian Thompson, as he shared in a video uploaded to X.

“I’m like, ‘Yeah, he’s being a wise ass’. . . I look out the cell, Luigi is standing there and he’s like, ‘Hey, how’s it going?’ Like, super nice. Introduced himself to me first thing. I’ve literally – I’ve been in the unit for 10 minutes,” Daddea, 29, recalled in the June 7 clip, which amassed over 80,000 views before it was deleted from his profile this week. 

Daddea was slapped with federal charges in February for allegedly 3D-printing more than 25 untraceable “ghost guns” – not unlike the firearm Mangione, 27, is accused of using to kill Thompson, 50, on a Midtown sidewalk on Dec. 4. 

The Tampa native only spent two nights in the federal lockup’s 4G unit before making $250,000 bail at his March 7 arraignment, according to the Brooklyn US Attorney’s office.

But he claims he, a fellow inmate nicknamed “V,” and Mangione wasted no time becoming buddies. 

“I go up and I go to shake Luigi’s hand, I’m like, ‘Yo, it’s an honor to meet you.’ . . . He turns around and he goes to me, ‘You two are the first kids that came in here who knew who I was or even cared about it,’” Daddea recalled.

“I guess he must have seen another white kid and he was like, ‘Finally,’” Daddea theorized in the clip. 

Mangione – who has been a “model prisoner” in his over 175 days of pre-trial detention, according to his lawyers – is a “collie,” which is a term used to refer to inmates with prison jobs, Daddea explained in the clip. 

“So a collie could be like a unit boss that tells you what cell you’re going to. Luigi just happened to be a collie that cleans the showers,” he said, adding that other “collie” jobs include preparing meals and cleaning food trays. 

When Mangione is not scrubbing the washrooms or running “laps around the unit,” he scours local news for his name, Daddea said. 

“Luigi gets the NewYork newspaper everyday . . . he would have me help look through some to see if there’s articles about him [sic],” he wrote in the comment section of the X video.

Daddea said he and Mangione, both Catholics, “did Ash Wednesday,” when a priest came in and put the charcoal crosses on their foreheads on March 5, and ate every meal together.

“So we sat together. Luigi would grab his sh-t and come sit with us every day. We would just eat, bulls–t,” he said. 

Daddea declined to comment when reached by The Post. 

In an electronic communication sent from jail on June 3, Mangione listed things he was thankful for – among them, the Bureau of Prisons’ music catalog, “Chicken Thursdays and Sweet Baby Ray’s bbq sauce,” and the thousands of books and letters people have mailed him. 

He wrote that his cellmate, J, “tolerates the clutter of all my papers, shares his unique wisdom, and doesn’t hesitate to humble me when I need it,” and that the MDC staff and correctional officers “are nothing like what ‘The Shawshank Redemption’ or ‘The Stanford Prison Experiment’ had me to believe” – despite “the occasional minor dissent.”

Mangione also thanked those who have donated to his commissary account, noting that their contributions have bought him a tablet, songs, stamps, hygiene products, barbecue sauce, Goya Sazón flavoring, peanut butter and tuna packets.

Mangione has pleaded not guilty to first-degree murder.