Charlie Day Still Knows Less Than You Think About His Own Super Mario Bros. Movie

It's been months since Mario and Luigi fans first learned casting announcements for the upcoming (and untitled) "Super Mario Bros." movie, but more details about the film are still completely under wraps. Big-name stars like Chris Pratt, Charlie Day, and Anya Taylor-Joy will headline the film, voicing Mario, Luigi, and Princess Peach, respectively (per Variety). Jack Black (Bowser), Keegan-Michael Key (Toad), Seth Rogen (Donkey Kong), and Fred Armisen (Cranky Kong) fill out the Mushroom Kingdom cast of characters.

The upcoming 2022 Mario film will be the first feature adaptation of the immensely popular series of Nintendo video games since 1993's "Super Mario Bros." According to Box Office Mojo, that film was an immense flop, grossing just under $21 million at the US box office on a $48 million budget. Neither audiences nor critics enjoyed that film, which starred Bob Hoskins as Mario and John Leguizamo as Luigi (via Rotten Tomatoes).

Nintendo announced the new movie's development in tandem with Illumination in 2018, but little information has surfaced about the film since then, save for casting details (via The Hollywood Reporter). Nintendo Enthusiast reported in August 2021 that actor Sebastian Maniscalco confirmed he would play a character named "Spike," reportedly based on a character named Foreman Spike from the 1984 video game Wrecking Crew.

Beyond that, little else is known about the movie — even Luigi voice actor Charlie Day is left in the dark.

Charlie Day compared secrecy surrounding production to the MCU

In a recent interview with Screen Rant, Charlie Day compared the "Super Mario Bros." film production to the Marvel Cinematic Universe. Apparently, Illumination and Nintendo are keeping plot details and the film's script secret even from Luigi himself.

"They released to me very specific lines, and they call me in and say, 'Say Mario 7000 different ways and then we'll pick which one we want,'" Day told Screen Rant. "So I know almost nothing... I'm not in the inner circle of the Nintendo World."

The 46-year-old actor spoke about the project recently on "Jimmy Kimmel Live," too, affirming the project's top-secret status. Day, who joked that he doesn't even really know if he's in the movie, even noted that he and Chris Pratt have not recorded lines together so far into production.

"Mario is probably in the know, but they don't tell Luigi anything," he joked (via YouTube).

The apparent secrecy surrounding the still-untitled Mario project follows an increasing trend in hotly-anticipated films and television shows in which productions often keep scripts and story details under lock-and-key. For example, rumors swirled that HBO filmed multiple endings to "Game of Thrones" to keep even its own cast unaware how the series would end (via Insider).

The "Super Mario Bros." movie is scheduled to release in theaters on Wednesday, Dec. 21, 2022 (per IMDb).