The production cast a wide net when it came to finding the right kid to play Sam's matchmaker son Jonah, and the young actors who came up during the search, per Carlson, included Elijah Wood, Joseph Gordon-Levitt, Ben Savage and Rider Strong, Jason Schwartzman and Joaquin (still going by Leaf) Phoenix—who, at 17, was quickly crossed off as too old for the part. 

The part eventually went to 8-year-old Nathan Watt. He was "frickin' adorable," casting director Laura Rosenthal recalled to Carlson, as well as Ephron's first choice.

But according to multiple accounts, after just a few days of filming it was clear that Watt—who had never been in a movie—wasn't going to work out. "The kid wasn't much of an actor," remembered on-site editor Bob Reitano, "but most importantly he couldn't remember his lines."

Watt, who starred in Unstrung Heroes with Diane Keaton a few years later but stopped acting in his teens, told Carlson that he didn't remember much about the experience, except for Rosie O'Donnell being funny and kind and Ephron being "abrasive." It was disappointing that it didn't work out, but, he added, "I was 8."

Enter Ross Malinger, who made his movie debut in 1990's Kindergarten Cop, as Jonah. "He was an 8-year-old who understood that there's a difference between saying the lines and playing around," Hanks told Carlson. "I don't know what it was, but as soon as we started work with Ross, it was the movie. Inexplicable."