"Benjamin is good, he's great," the Draft Day star told Jimmy Fallon on the Tonight Show Wednesday, April 9. "I get home Friday and he leaves that day for Batman. I know, it's going to be awful, though, because he's been home now for a few months and when he's really home, he's so in dad mode and I think he's going to have a hard time."
"So he's been Mr. Mom when he's home?" Fallon quipped, to which Garner responded with a simple, "hmphhhh!"
Laughing, she told the show host, "We are divided down a very mom-dad [line]. If it has to do with making food, or homework or anything that has to do with actually functioning, that's a mom thing. Then coming in, just as you're getting them to bed and picking them up by their heels and swinging them around? That's a dad thing. Anything fun, that is Ben!"
The actress added that her husband has been "psyched to finally have a little boy,” and has a special bond with their 2-year-old son, Samuel. "He LOVES his girls [daughters Violet, 8, and Seraphina, 5], but he's serious about his son right now. So, he taught him about his bits," she said. "He taught him about his 'P' and his two 'N's.'"
"Now anytime we pass a dog who's walking on the street or we're at a zoo or something, our poor little son is crouching down and looking up and he's like, 'Mama, does that have a vagina or a penis and two nuts.'"
With Fallon cracking up, Garner quipped, "That's what Ben's been up to."