Today, Two and a Half Men is still best-remembered as the sitcom that starred Charlie Sheen, Jon Cryer, and Angus T. Jones as the titular trio of two adults and one youngster.

But the cast did undergo several changes in the latter half of the sitcom's 12 season run (2003 to 2015). Most notably, Sheen was fired from the show in the middle of season 8. Afterward, Two and a Half Men went into recovery mode in an effort to salvage the popular series following the exit of its star.

The answer was Ashton Kutcher's character, "Walden Schmidt." But how did we get there?

'Two and a Half Men': Why Did Charlie Sheen Leave The Show?

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Two and a Half Men: Charlie Sheen was fired in season 8

Devoted fans of Two and a Half Men will remember that the production of season 8 was put on hold after Sheen, who starred as "Charlie Harper," entered rehab. But "winning!"-era Sheen also got himself into predicaments with a series of controversial interviews — including one where he bashed Two and a Half Men creator Chuck Lorre.

The actor was fired soon after, and documents surrounding the decision revealed that his substance abuse problems were causing major problems on set and rendering him unable to perform his role. Sheen, however, denied aspects of this characterization. (For much more, see: Why Did Charlie Sheen Leave Two and a Half Men?.)

Two and a Half Men cast changes in season 9

Before season 9 arrived, news broke that Ashton Kutcher was cast as a new major character who would shoulder the load of Sheen's absence. "I can't replace Charlie Sheen but I'm going to work my ass off to entertain the hell out of people!" Kutcher was quoted as having said at the time.

Season 9 opened with news that "Charlie Harper" had died in a train accident, so the "Harper" house went up for sale. Billionaire "Walden Schmidt" (Kutcher) purchased the home and moved in alongside "Alan" (Cryer) and "Jake" (Jones). This season premiere episode was titled "Nice to Meet You, Walden Schmidt."

Two and a Half Men: Ashton Kutcher's era as "Walden Schmidt"

While overall reception of Kutcher's "Walden" was mixed, his arrival on the show did give Two and a Half Men its highest ratings and ultimately bumped the show up a time slot on CBS. The cast and showrunners also highly praised Kutcher, saying he "saved the show."

Angus T. Jones later left amid more high-profile criticism of Two and a Half Men after season 10, leaving just Kutcher and Cryer for the final two seasons.

RELATED: Two and a Half Men - "Jake Harper" in 2020

Jon Cryer, Ashton Kutcher, and Angus T. Jones in 2011.

The former That '70s Show star's transition also led some to observe a shift in tone over the final four seasons of Two and a Half Men. Highlights with "Walden Schmidt" included his close friendship with much of the cast, his short-lived marriage to "Alan," and the pair's adoption of "Louis" in season 12.

Kutcher remained with the show through its season 12 finale, which aired in 2015.

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Ashton Kutcher in a promo photo for Two and a Half Men season 10.
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