"It signifies I'm getting older," Mr. Cusack, himself still childless, said with a laugh during a recent interview.
The 41-year-old actor, though, appeared remarkably the same as he did in 1990's The Grifters .
"I don't feel any different," he said, smiling. "Recover a little slower, but that's about it."
Mr. Cusack stars in Martian Child , which opened Nov. 2, as a science fiction writer who adopts a shy, eccentric boy. Next month comes Grace is Gone , a Sundance Film Festival hit in which the actor portrays a former soldier who takes his daughters on a road trip to delay telling them that their soldier mother has died in Iraq.
In Martian Child , he essentially keeps his usual screen persona: witty, aloof, idiosyncratic. It's easy to envision his character as the grown-up version of Lloyd Dobler in 1989's Say Anything or the slightly older incarnation of Rob Gordon from 2000's High Fidelity .
In Grace is Gone , though, he gives a quiet and grief-filled performance for which he's getting considerable buzz, courtesy of a Harvey Weinstein-orchestrated Oscar campaign.
The duality of the roles is typical of Mr. Cusack, who tends to alternate between studio pictures (1997's Con Air , 2001's America's Sweethearts , 2005's Must Love Dogs ) and more offbeat indie fare (1999's Being John Malkovich , 2002's Max ).
"I keep trying to explore stuff that I like and balance the business with personal passions," Mr. Cusack explained.
Clearly differentiating between the motivations behind Martian Child and Grace , he said: "One the studio wanted me to do, and the other was a script I really loved."
Not one to ever totally go Hollywood, Mr. Cusack has referred to fame as a "24-hour petting zoo" and lamented how studios view him as a "brand."
"It's only when you try to get jobs or get certain things made from the studio that you realize what that is," said Mr. Cusack, who speaks barely above a whisper.
"You just understand it when people tell you 'No.' It's mostly just more what they think will make money. That's really it. 'Can we get Johnny Depp?'
"I'm interested in doing stuff that people I admire do, which is try to explore being human and admit that you're human," he said. "At least admit it in film, if you can't do it everyday in life."
Grace is Gone (for which he was also a producer) reveals a new dimension to the actor. Writer-director Jim Strouse (who wrote 2005's Lonesome Jim ) wrote the part with Mr. Cusack specifically in mind.
"I just thought it required some things I knew that he could do but hadn't been asked to do," Mr. Strouse said.
"He's got so much energy in life and on screen and he kind of can't contain himself. I just thought it would be interesting to see him say very little -- kind of the opposite of everything he's known for and so good at.
"He was really excited," Mr. Strouse added. "When I first met him, his enthusiasm reminded me of a child almost."