CBS announced that the couple will appear on the sitcom together.
Kunis will play the character Vivian, a young woman that show up at Walden’s door, right when he prepares to propose to someone else.
Rumors of an engagement between the two have circulated for a while, and last week a source confirmed to People that Kutcher popped the question.
The actress was also seen wearing a diamond ring recently.
The couple began their relationship in 2012.