"My first real kiss ever was with him on the show," Kunis tells W magazine for its August issue, on newsstands July 9.
"And when That '70s Show had a prom, my date for the prom turned out to be my fiancé. We can honestly say that we went to prom together!" she says. "I do think that in that episode I went home with someone else. We don't talk about that part."
The actress, 30, says when she was younger, she never thought she would get married, but "I found the love of my life," she says. "We all get movie star crushes. I'm marrying mine."
Kunis says she plans to keep her wedding secret and private, and the pair are eagerly awaiting the arrival of their first child, a girl, this fall.
"I have never wanted to be the person who only has business on her mind," she says. "To me, this job has always been a hobby that turned into a great profession, but I don't eat and breathe acting. I'm sure Meryl Streep has a very different point of view. But I'm excited about being a full-time mom."