The actor pointed out Thursday night that there was "magic in my wife's belly" when he retweeted a picture showing him and her at a Disney on Ice skating party with Michael, 10, and Ava, 8, in tow.
In that shot -- it's different from the one above -- McGinn's baby bump is clearly visible.
"I love big families ... ," the "Saved by the Bell" star told People at the event. "Waking up in the morning and seeing their faces when they see the gifts ... all holidays are so much more special with children."
While telling People that kids make life better, however, the "Franklin & Bash" alum shared one caveat: "Not at the beginning," he said, "but as they sleep through the night, that makes life better."
With a fourth child on the way, Gosselaar definitely knows from experience.