On the large billboards plastered all over town promoting this weekend's release of "The Switch," A-listers Jennifer Aniston and Jason Bateman are touted as the film's main attraction.

But according to many critics, the real star of the romantic comedy is Thomas Robinson, an 8-year-old Valley Village resident who plays Jennifer Aniston's precocious and endearingly neurotic son.

In her review of the film this week, Times critic Betsy Sharkey praised the actor's "excellent job" in the movie, calling him "talented and adorably soulful."

After spending a night observing Thomas during his first big Hollywood movie premiere earlier this week, we can vouch for that. Thomas -- who was only 6 when he filmed "The Switch" -- is about as un-Hollywood as it gets. Too shy to speak to reporters on the red carpet, he timidly posed for pictures and attended the premiere's swanky after-party, where he sat with his family for about an hour before asking his mom if they could go home. (Check out this photo diary of his big night.) What struck us most about him is how much he truly seemed to embody the character he plays in the movie: honest and even a little sad.

Bateman echoed that sentiment: "I don't want to take anything away from his acting talent, but he was similar to that part in his sweetness and kindness and his accessibility," the actor told us in an interview earlier this year.

Of course, Thomas is only one of the young actors who has popped up on the big screen this summer, when it seems there have been a wave of strikingly naturalistic and evocative performances from kids in films like "Ramona and Beezus" and "Flipped."

But just how do casting directors track down the perfect child actor, who is not only cute and talented, but capable of handling the pressure? That's one of the questions we explore in our Sunday Calendar story, in which casting directors, filmmakers and former child stars weigh in on the challenges of working in Hollywood as a youngster. Douglas Aibel, the casting director who found Thomas for "The Switch," said he could sense early on that the young boy was overwhelmed by the audition process.

He was never a big movie star, but in addition to his signature role as Arnold on TV's "Diff'rent Strokes," he did make a couple of features, including "Jimmy the Kid" and "On the Right Track," as well as TV movies such as "The Kid with the Broken Halo" and, as die-hard San Diego Padres fans will recall, "The Kid from Left Field." And of course he helped shape the tastes of any film and pop-culture fan who grew up in the 1980s. Clips and a walk down memory lane below.

-- Steven Zeitchik