Constantine, 14, and Nicoletta, 8, Lekas, of Elmwood Park, were let on the movie's Jersey City set Friday, where a big scene was filming at the Loews theater.
The Lekas siblings mingled with the cast and crew and even hang out with the movie’s director Todd Philipps.
The Warner Bros. Pictures movie starring Joaquin Phoenix is intended to be the first in a series of DC-based films separate from the shared DC Extended Universe.
Filming began in New York City in September -- where lead actor Phoenix was spotted in full Joker makeup running from Gotham cops -- before moving to Jersey City and Newark.
The siblings have been longtime fans of the Batman, and went to go watch when dad Harry Lekas got a call from a nearby friend saying that the movie was filming right outside his hotdog grill, Boulevard Drinks.
He says the kids -- who dressed up as the Joker for Halloween -- were thrilled to be part of it all.
"They got to mingle with the cast and crew that evening and everyone was super friendly," Lekas said.
"They took plenty of pictures together but the highlight of the evening Was getting to hang out along side the movie director Todd Phillips as he was directing the scenes."
The Warner Bros. movie is set to be released in October 2019.
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