The more lighthearted tone of the new “Justice League” (opening Friday) suits Ezra Miller, who returns as The Flash/Barry Allen. “It was a blast to improvise so much and get to try some of my weird ideas about choreography and other unconventional things in the film,” the actor told me in an interview in London. “But I really felt especially lucky because I believe I got to deliver some of the funniest, craziest lines in the script.” Offbeat humor closely matches Miller’s own personality, “and it’s something I also bring to my performances with my band, Sons of an Illustrious Father.” The entertainer said that his music is just as important to him as his acting career, and he made a point of noting “one of the best audiences and venues we played this year was in Chicago,” calling the Tonic Room “perhaps my favorite place to perform, ever! Plus, I find Chicago audiences also have a great sense of humor, so I’m assuming they’ll love ‘Justice League.’ “No, that gig in Chicago was a fantastic experience. I’ve been a New Yorker a lot of my life, but Chicago is a really dope town. That windy element you’ve got going there is a genuninely unfortunate fact, but I must say you people do deal with it well.” Co-star Ben Affleck said humor is perhaps more evident in “Justice League” than it was in his earlier outings as Bruce Wayne/Batman, especially in “Batman v. Superman: Dawn of Justice.” “What’s part and parcel of this film is having all these different superhero personalities coming together,” Affleck said. “I do love how we see Henry Cavill’s Superman express his dry wit. I get to show even more of Bruce Wayne’s wry sense of humor here. And Ezra Miller’s The Flash? He steals every scene he’s in — and for good reason. He’s brilliant!”