The Hollywood hunk is set to romance veteran 'Taxi' star Marilu on the season finale of the CBS sitcom, despite her being 25 years his senior.
Ashton's character Walden will land himself in hot water after he becomes smitten with cougar Marilu, who plays the grandmother of one of his girlfriends in the episode airing on May 9 in the US.
Disney star Hilary Duff has been confirmed to guest star as Walden's unsuspecting girlfriend, Stacey, TV Line reports. This will be the 'Lizzie McGuire' actress' first silver screen role since giving birth to her son Luca in March 2012.
The show's star Jon Cryer praised her acting skills and said she had ''fantastic'' comic timing in front of the live studio audience.
He explained: ''She plays a motor-mouth character, so they gave her page-long monologues. She was lovely, and we had a great time.
''All week, she was on book [looking at the script] which is understandable. But even when we got within two hours of the show, she was still on book. We were thinking, 'Oh no, Miley better bring it!'
''And then we did it in front of the audience, and Miley brought it! Miley was just on fire and fantastic.''