The actor initially played coy when Rosenbaum brought up his baby on the way. "What? I do?" he asked, before Rosenbaum assured him he heard the news from Jessica, and Tom called for his wife to confirm.
"You lying bastard!" Rosenbaum joked to his former Smallville co-star. "But you do! You have another one coming!"
Tom and Jessica's first child, Thomson, has already brought them a lot of joy.
"He's a good, cute, funny kid," Tom said of his son, who he called "hilarious." "He makes me laugh all the time."