Heath Ledger's family attended Monday's The Dark Knight premiere in New York, where the late actor's father left the theater giving a thumbs-up sign.

Kim Ledger and his wife Ines – Heath's stepmother – bypassed the red carpet and ducked into the theater to watch his late son play The Joker in the latest Batman film.

Also attending the premiere were Heath's mother Sally Bell and her husband, and Heath's older sister, Kate.

As his father Kim left, he was asked how it felt to attend, responding with the thumbs-up. He also told reporters it was "very good."

Heath Ledger's costars, meanwhile, used the occasion to pay tribute to him.

"Working with Heath was fantastic," said Christian Bale, 34, who reprises his role as the Caped Crusader. "He steals the movie and I'm quite happy to say that. He's a hell of a talent and created a joker that's very iconic and one that will become a classic portrayal of the ages."

Michael Caine, 75, who plays butler Alfred Pennyworth in the film, which opens July 18, noted the "intensity and ferocity of the performance."

"But when we were sitting down between takes, he was completely ordinary," Caine added. "He wasn't preparing himself or saying 'Please leave me alone, I've gotta do this.' Instead he was talking to me.

"We would sit and chat and have a cup of coffee, then suddenly they'd say, 'We're ready, Heath,' and he'd go straight into The Joker," Caine continued. "His energy was astonishing, especially when it came from this kind of calm. He's certainly the best villain I've ever seen."

Melbourne-based Robert Collins, a Ledger family friend for 30 years and co-executor of the Ledger will, told Who magazine in Australia he saw The Dark Knight preview in Perth last night and described it as "a eerie feeling" watching him.

"I am aware that Kim Ledger and the family are over in New York for it, it was something they felt they had to do and it was a personal thing from their point of view," said Collins.

Ledger, who died of an accidental prescription-drug overdose on Jan. 22 has garnered Oscar buzz for his role as the smiley yet sinister Joker. Anticipation for The Dark Knight has been at a fever pitch with midnight shows having sold out so quickly that theater owners have had to continue to adding 3 a.m. and 6 a.m. showtimes.