Bruce Willis (search) and Ashton Kutcher (search) -- Demi Moore's past and present husbands -- are such good friends they will appear together for the first time on an episode of "That '70s Show." (search)

In a silly twist, the episode is marriage themed.

According to FOX, as Red and Kitty celebrate their 25th anniversary, Kelso (Kutcher) gets bitten by the marriage bug and decides to propose to Jackie.

But Vic (guest star Willis), a sketchy fast-talker with a bad toupee, makes Kelso a job offer he "cannot refuse."

Kutcher and co-star Topher Grace are the first two cast members to leave the show -- entering its eighth season Wednesday night.

Next week will be Kutcher's last regular appearance on the series.

On the show, Grace's character has moved to Africa.

In real life, both are focusing on careers in films. Kutcher, 27, has already become a big-shot producer as the brains behind hit shows like MTV's "Punk'd" and is working on a network sitcom based on his life with Moore.

He married Moore, 42, in September.