Whatever you do, don’t ask Sylvester Stallone — Mr. Stallone to journalists everywhere — to read off a teleprompter.

Stallone stole the show at the Paramount+ U.K. launch on Monday, where the star of mob drama “Tulsa King,” faced with a teleprompter like his fellow actors in attendance, went dramatically off-piste and opted to “speak from the heart” for 10 minutes, delightfully throwing a wrench in an otherwise perfectly curated showcase.

“I’m not going to read that. I’m not,” boomed Stallone to cheers from the audience of around 200. “I’m going to read from the heart!”

In a rambling speech, Stallone touched on his love of franchises — “When I first started a franchise, they said, ‘Oh very careerist. You’re going to make the same movie three, four times?’ It’s like, ‘Yeah'” — through to riding horses, his own early career, and ultimately “putting together this new gang of misfits.”

“I’d like to say I did it all on my own,” joked Stallone, before thanking Paramount boss Bob Bakish; Chris McCarthy, president of Paramount Media Networks; as well as Tom Ryan, president and CEO of streaming.

Stallone was the final act in an hour-long presentation that dazzled the audience at Outernet, a new media space on Charing Cross Road in central London, whose massive screens for walls were put to good use by Paramount. The studio hosted media and select producers and partners at a lavish party for the service, which formally launches in the U.K. on Wednesday (June 22) with an 8,000-hour content offering spanning movies, TV shows, new originals and library fare.

Hosted by Graham Norton, who presents drag singing competition “Queen of the Universe” for Paramount Plus, a cavalcade of celebrities took to the stage, introducing one another and singing the praises of their shows and the platform. After a full day of press beginning at 9 a.m., most were, perhaps understandably, reading off a teleprompter, but that didn’t stop outliers like Stallone, who relished in a bit of improv.

In total, 21 actors took the stage, including Matthew Goode, who presented making-of-“The Godfather” series “The Offer”; the cast of “Teen Wolf: The Movie,” including Tyler Hoechlin and Tyler Posey ; “Yellowjackets” actors Melanie Lynskey and Tawny Cypress; “The First Lady” trio Gillian Anderson, Viola Davis and Michelle Pfeiffer (although, bafflingly, only Anderson was appointed to speak); “Halo” stars Pablo Schreiber and Natasha McElhone; “iCarly’s” Miranda Cosgrove; “1883’s” real-life couple Tim McGraw and Faith Hill; “The Man Who Fell to Earth” actors Chiwetel Ejiofor, Bill Nighy and Naomie Harris; “George & Tammy’s” Jessica Chastain and Michael Shannon; “Star Trek” actors Sonequa Martin-Green and Kate Malgrew; “Bass Reeves” star David Oyelowo; and “Yellowstone” lead Kevin Costner, who drew cheers from the crowd.

“Cinematic storytelling is what Paramount does,” said Costner. “Now, Paramount is taking that incredible movie legacy and bringing the same approach to television – pushing TV and streaming to where they’ve never gone before with ‘Yellowstone’ leading the way.”

McGraw and Hill, the stars of “Yellowstone” prequel “1883,” also received a warm response in the room.

“What you see is not special effects – the horses, the river crossings, the fights,” said McGraw. “It’s all real, designed to take you into the heart of the American west. And the challenge is what excited me — because I knew that if we could get it right, we’d be creating something totally new.”

Hill added: “Filming this series has been unlike anything Tim and I have ever done. And it’s been worth every second because we’re creating something that audiences have connected with so deeply.”

Elsewhere, “Halo” star Pablo Schreiber said he was part of a franchise that “has touched generations.” Indeed, “Halo” is believed to be the top driver of acquisitions, consumption and engagement for Paramount+’s international markets since the streaming service launched in March 2021.

While Paramount boss Bakish wasn’t at the event, Ryan was on hand to open the showcase, declaring that the new service — which unites Stallone, SpongeBob SquarePants, “Star Trek” and “South Park” in one place — is “what a streaming service is meant to be.”

Meanwhile, Maria Kyriacou, president of Australia, Canada, Israel and the U.K. for Paramount, highlighted the plethora of British content on the platform, such as “Sexy Beast” and “A Gentleman in Moscow”: “Launching Paramount+ in the U.K. is not just about bringing the best of the world to Britain, it’s about getting even more of the best of Britain to the world.”

The service commissioned 20 shows prior to launching, and the former ITV Studios executive promised “more to come.” The service revealed on Monday that it will make 150 international originals by 2025. In the U.K., Paramount+ will retail for £6.99 ($8.50) per month. (It will be freely available to subscribers of Sky Cinema.)

Paramount+ launched in South Korea on June 16 and will next expand to Italy in September, and to Germany, Switzerland and Austria and France in December. The platform is expected to launch in 45 markets by the end of the year.