Back up on the big screen as The Hatbox Ghost in Disney's remake of Haunted Mansion, as ever, Leto went the extra mile when it came to bringing this apparition to vivid life for director Justin Simien.
"It's part stunt person on set, it's part CG, it's part motion-capture and it's part Jared Leto's brilliant vocal performance," the latter told Metro.
"His physical performance was captured and kind of translated on top of what we had done on set already. It was a wild thing to come together – actually, it was quite like animation – and amazing to see Jared Leto so dedicated to this character, down to what he had in his mouth!"
Apparently, the Blade Runner 2049 star applied a pair of fake teeth "that you would never see", but they came to shape the way he spoke, dressed and even prepared for the role.
For anyone who's closely followed Leto's electric career thus far, you'll know that this is a tried-and-tested approach to his work in Hollywood.
Cast your mind back to 2000's hellish drug drama Requiem for a Dream - in which he played heroin addict Harry Goldfarb - Leto not only shed 25 pounds and slept on the streets of New York City, he also went abstinent from sex to give his character's suffering another level of authenticity.
He admitted during an interview with the BBC: "I was in a constant state of hunger like my character. I was miserable. It was a painful, dark place, but it was rewarding.
"There were a couple of moments towards the end where I had hallucinations. I'd look up at the sky and I'd get a feeling of complete serenity."
Seven years later, he took on the part of Mark David Chapman (real-life killer of The Beatles icon John Lennon) in the movie Chapter 27.
60 pounds of added weight was where he went with this one, but the physical ramifications were enough to put Leto off for life.
"I'd never do it again," he shared with Digital Spy around the time of its release. "Towards the end of the shoot, one of the glaring issues was the pain I had with my feet. I couldn't walk for long distances; I had a wheelchair because it was so painful.
"My body was in shock from the amount of weight I gained. It took about a year to get back to a place that felt semi-normal."
Then there's the gig which earned Leto that prestigious golden statuette: Dallas Buyers Club.
To portray trans HIV patient Rayon opposite Matthew McConaughey's real-life pharmaceutical smuggler Ron Woodroof, the 51-year-old waxed and shaved his whole body alongside a dramatic 40-pound weight cut.
"For me, it was about how it made me feel, how it made other people treat me," he reflected while speaking to The Guardian.
Prior to shooting, which Leto spent the entirety of in character, he "road-tested" Rayon on the public.
"You kind of have to register reactions and things. To get a little judgment, some meanness, a little condemnation was a useful thing for the part. I went to Whole Foods Market to, I guess, just stare at the food, because I certainly wasn't eating a whole lot of it.
"I got three distinct looks from people. One was, 'What is that?' The second one was, 'Who is that?' and the other was, 'I dunno what the f*** that is but I don't like it.'"
Outlandish presents for his co-stars Margot Robbie and Will Smith were widely reported - including bullets, anal beads, a dead rat, and used condoms - to "create a dynamic and spontaneity" that would mirror the chaos of his Clown Prince of Crime.
Much of this was eventually dispelled, though, when the actor told Entertainment Weekly: "Any of the very few gifts that were ever given were given with a spirit of fun and adventure and received with laughter, fun, and adventure.
"I'm playing a guy called The Joker, it's okay to play some jokes. I'm an artist at the end of the day. If I do something risky and you don't like it, basically, you can kiss my ass."
Meanwhile, the mesmerising sequel Blade Runner 2049 saw Leto wear clouded contact lenses in order to experience Niander Wallace's blindness.
"Everybody became super silent, and there was a kind of sacred moment. Everyone was in awe."
For legendary filmmaker Ridley Scott's 2021 biographical crime flick House of Gucci, he went hard.
"Bringing Paolo [Gucci] to life was like birthing a bowling ball out of my sphincter," Leto bizarrely revealed to i-D.
"It was a very physical performance. I did it all. I was snorting lines of arrabbiata sauce by the middle of this movie. I had olive oil for blood. This was a deep dive I did. If you took a biopsy of my skin, it would come back as parmesan cheese! This is my love letter to Italy.
"I had an Italian accent and I enjoyed and embraced that, and lived in that space as much as I could, and for as long as I possibly could."
Fortunately for his colleagues, Leto didn't go full-bloodsucker for last year's Spider-Man spin-off Morbius, but he did choose to realise the physical depreciation of Dr. Michael Morbius when the cameras weren't rolling.
His laboured movements were stalling production so much that the crew ended up bringing in a wheelchair to quicken things up.
Commenting on the megastar's divisive process, director Daniel Espinosa shared with Uproxx: "I think that what Jared thinks, what Jared believes, is that somehow the pain of those movements, even when he was playing normal Michael Morbius, he needed, because he's been having this pain his whole life. Even though, as he's alive and strong, it has to be a difference.
"I think it's really mysterious, what they do. Almost all actors, in general, have their own reputation of being an interesting person how he works with their characters. I think that all of them have these traits. If you want a completely normal person that does only things that you understand, then you're in the wrong business."
Watch: Jared Leto dresses up as Karl Lagerfeld's cat for 2023 Met Gala