A secret admirer of Luigi Mangione snuck a heart-shaped note to him in a pair of argyle socks he was allowed to bring to his latest circus-like court appearance, a new legal filing reveals.

“Luigi, we are rooting for you! Keep your head held high and know there are thousands of people wishing you luck,” read the note, which was “secreted” in cardboard that the pair of fresh socks were wrapped around, according to a filing Wednesday from Mangione’s lawyers.

The note was signed “R/Free Luigi,” a reference to a page on the website Reddit that is devoted to Mangione’s case.

But the accused killer — and heartthrob to his legions of googly-eyed groupies — refused to wear the socks at the February hearing because he felt they “didn’t look good,” the court docs from the Manhattan District Attorney’s Office state.

Prosecutors also revealed new details about Mangione’s arrest at an Altoona, Pennsylvania, McDonald’s — including that the suspected assassin was carrying four zip-ties, a roll of black duct tape and a blue Polaroid camera when cops nabbed him.

Law enforcement recovered personal grooming equipment in fashion-conscious Mangione’s black backpack as well, including a hair trimmer, tweezers and nail clippers, the filings released Wednesday show.

The Manhattan DA’s Office pushed back on Mangione’s claims of unfair treatment — noting he’s actually getting “special treatment” by being allowed to change out of jail garb for his court appearances.

Court officers uncovered the love note — and a second hidden note addressed to “Joan” — inside a bag of clothing provided by Mangione’s defense counsel ahead of his Feb. 21 hearing, according to the filings.

“Thank you so much for trusting me and helping me navigate this entire disservice,” the message said. “You are amazing and I am grateful!”

Prosecutors did not reveal the “Joan” in question.

A PR pro, Joan Vollero, has been working as a spokeswoman for Mangione’s legal team at the New York-based Agnifilo Intrater LLP law firm. She declined to comment Wednesday when asked if she was the mystery “Joan” referenced in the second heart-shaped note.

Mangione’s lawyers claimed ignorance of the secretly slipped notes in a filing Wednesday night.

“In the haste of the situation, the defense inadvertently did not see that there were two heart-shaped notes contained within the socks,” the filing says. “This was obviously inadvertent as one of the two heart-shaped notes was not even addressed to Mr. Mangione,” the filing adds. “The District Attorney’s Office ostensibly realized the innocent nature of this event, and that it was not a genuine danger or concern, as they did not bother to alert the Court at the time.”

The court papers also argue the DA’s office raised a stink about the notes to “deflect” from Mangione’s “reasonable and standard requests” for evidence in the case and for him to be able to use a laptop in jail.

Prosecutors warned that future contraband smuggled into the alleged murderer’s clothing could put court officers at risk.

“Fortunately, the items smuggled were handwritten notes and not contraband capable of harming the transporting officers,” the filing reads.

Mangione’s decision to go sockless with bare ankles sent his thirsty fans into a frenzy.

He has pleaded not guilty to charges that he killed UnitedHealthcare CEO Brian Thompson in cold blood on a Midtown sidewalk Dec. 4, 2024.

Mangione’s attorneys said in papers filed Monday that they wanted him to have access to a laptop in jail so he could properly prepare for trial. 

The laptop would solely be used for viewing case evidence like videos, including witness interviews, photos and 15,000 pages of records, according to the filing.

But Manhattan DA Alvin Bragg’s office warned Wednesday that Mangione could share the footage from the laptop if he has “unfettered access” — even suggesting that witnesses could be intimidated by his crazed fans.

“The acts of those who sympathize with defendant show that nobody associated with the case is off limits to acts intended to intimidate and coerce,” prosecutors said.