Child star Jacob Tremblay had no problems pretending he was Julia Roberts' kid in hit new movie Wonder, because she made him feel so comfortable on set.

The young Room star was a little nervous about acting opposite the Oscar winner, who stars in one of his favorite films, Hook, but she quickly put him at ease and became just like a second mother even before cameras rolled.

"She was already so comfortable with me the first time we met," he tells Access Hollywood Live. "It was so easy to pretend that she was my mother.

"She's a real mother and she's always so motherly. It's something great about her."

Jacob, who got to meet Julia's three kids, also enjoyed having Owen Wilson as his movie dad, revealing the actor once cursed on set when he stubbed his toe in a scene.

"He fell to the ground... and said a curse word," the 11-year-old laughs, explaining Owen apologized afterward.

Tremblay also revealed he's getting a lot of support for the new film at school - his fellow sixth graders are all taking time out to go and see the movie, in which he plays a boy with a rare genetic facial condition.

He expects to see a few tears, because he cried while watching a screening, adding, "but not as much as my mom cried".

Jacob also had to tear up on camera, but admits he finds emotional scenes quite easy.

"I actually like doing crying scenes because it's real acting," he adds. "It's the actual acting part."

His acting impressed Julia who is singing her young Wonder co-star's praises around Hollywood, telling CinemaBlend he stayed in character as Auggie throughout the shoot - and she never saw the young star without prosthetics.

"I did hear from the make-up guys, that he sat and was still and patient and never complained," Roberts said. “I would have been like, 'Okay, come on, people! Can we just...' He never complained on the set, and he never complained in the chair, and that, I think, speaks to who he is as a human."