(Cover) - EN Showbiz - Justin Timberlake thought it "weird" that Olivia Wilde played his mother in his new film.

Justin stars in science fiction thriller In Time. Olivia, who is 27, plays his mother.

The co-stars were thoroughly amused by their characters' age difference.

"[Olivia is] actually three years younger than me, which made it even weirder," Justin told USA Today. "We laughed about it a lot. It doesn't matter who it would have been, it would have been awkward."

The bizarre generation gap was engineered purposely by casting directors. In the movie, the ageing process has been eliminated altogether. Olivia's persona has actually reached the midlife stage in the movie.

"It's one of the visually jolting moments in the film when I walk into the kitchen and say 'Good morning, Mom,' and she says that she's turning 50," Justin recalled. "The audience gets a good chuckle. It's visually perverse."

The pair - who met while filming Alpha Dog in 2006 - shared a lot of laughs with each other, but remained focused on task. While filming Justin and Olivia were thoroughly invested in their characters.

"We could laugh about it and then we had to establish the relationship."

In Time will be released in the US today. (C) Cover Media