Five years after "Joker" took home the top prize at the Venice Film Festival, director Todd Phillips can't help but feel a bit anxious about returning with its sequel.

"Joker: Folie a Deux," one of the festival's most anticipated films of the 81st edition of the festival, premiered Wednesday and theatergoers at the Sala Grande theater gave the movie and stars Joaquin Phoenix and Lady Gaga an 11-minute standing ovation.

"It feels right, it feels correct to be back in Venice. It felt like the logical launching off point for us," Phillips said ahead of the premiere. "On this one I’m a little more nervous. It’s a lot easier to come into something as the insurgent rather than the incumbent."

A sequel was more a joke than an inevitability to Phillips and Phoenix while making the first movie. For one, Phoenix is not the kind of actor to jump at a "franchise." But then an idea emerged to explore the music that Phoenix's character, Arthur Fleck, is hearing in his head. It would have to be as bold, unexpected and audacious as the first, they thought.

That first film had resonated in a way that no one quite expected: It made over $1 billion at the box office and won Phoenix the best actor Oscar. One of its fans was Gaga, who said that it "really deeply moved me" and showed her something she had never seen before.

The streets outside the Sala Grande theater were packed with Gaga fans hoping to catch a glimpse of her on the red carpet. Gaga arrived wearing a Christian Dior Haute Couture gown and an elaborate Philip Treacy headpiece that was evocative of a funeral veil.

"Joker: Folie à Deux" finds’ Phoenix’s Arthur Fleck institutionalized and awaiting trial for his crimes. The last film ended after he shoots late night host Murray Franklin (Robert De Niro) on live television, which has made him a God to a certain set, including Gaga’s Harley Quinn who he meets in a different ward. The two fall immediately in love and take to song to express themselves.

Both Phoenix and Gaga sang live for the film, with a pianist just off camera who, she said, felt like another actor in the scene in a way.

"For me it was kind of about unlearning technique and forgetting how to breathe and allowing the song to come completely out of the character," Gaga said. "It gives the characters a way to express what they need to say."

Phoenix, who initially balked at the idea of singing live, added: "Part of the joy at least for me was taking these songs that were standards and trying to find a way that they were specific to the characters."

They also learned various choreography over the course of months for several different numbers, including a waltz in the rain. But even with the training and practice, they said, things had a tendency to change in the moment.

"We all really thrived in the moment and in the chaos of it all," Gaga said. "We had to find it every day. What was the truth of the scene, what was the honest moment."

She added: "You can learn a song, learn a routine for a dance ... but that’s not always the most honest thing to do on camera."

Phoenix recently made headlines for leaving a Todd Haynes film several days before it was to start shooting. He declined to elaborate on the situation, saying it wouldn’t be fair to the other creatives involved who were not available to comment. He also said he didn’t want to focus on the weight he lost to play Arthur Fleck. During the press tour for the last film, he regretted speaking about it so much.

Gaga made a grand entrance to the Lido on Wednesday several hours before the red-carpet premiere. Fans and photographers clamored around the docks outside of the Excelsior Hotel hoping to catch a glimpse of her arriving. She popped her head out of the private water taxi, alongside Phillips and Phoenix, as fans nearby shouted "Gaga! Gaga! Gaga!" in unison.

On the dock, she blew kisses to the excitable fans, stopped to sign several autographs, and accepted flowers from one eager onlooker. She wore an elegant black Dior Haute Couture dress, beret and sunglasses offsetting her blonde hair.

In a festival lineup full of major Hollywood stars, including the likes of Angelina Jolie, George Clooney and Brad Pitt, Gaga is in a class of her own with her knack for creating a memorable red carpet moment.

Six years ago, for "A Star Is Born," she made a splash playing the part of the movie star - and gave the festival some of its most iconic shots in recent memory. Remember her perched on the side of the private water taxi in that black Jonathan Simkhai bustier dress, blowing kisses to fans and photographers? Or her show-stopping pale pink feathered Valentino Couture gown that seemed to pop even more against the rainy backdrop?

Reviews for the new film will be out in a few hours, which could dictate the trajectory of the film for months to come and whether or not it is once again an Oscar contender or another billion-dollar box office hit.

The Joker sequel is competing again for the festival’s main prizes against the likes of Pedro Almodóvar’s "The Room Next Door,"

Pablo Larraín’s "Maria" and Halina Reijn’s "Babygirl." Awards will be presented on the final day of the festival, Sept. 7.

"The hard part of this is you feel eyeballs on you," Phillips said. "You just have a different pressure."