They both share a co-creator and were two of the biggest sitcoms of the last 20 years, but do Two And A Half Men and The Big Bang Theory share a universe? Two And Half Men debuted in 2003 and followed Jon Cryer's luckless Alan as he and his son Jake (Angus T. Jones) moved in with Charlie (Charlie Sheen), Alan's womanizing musician brother. The show wasn't greeted with warm reviews, but it became a major ratings success, and ultimately ran for twelve seasons before ending in 2015.
Two And A Half Men was co-created by sitcom and vanity card king Chuck Lorre, alongside Lee Aronsohn. He also created The Big Bang Theory with Bill Prady, with the CBS series arriving in 2007. The sitcom followed a group of genius friends who also have little to no social skills and Penny (Kaley Cuoco), a waitress they befriend. Like Two And A Half Men, the mixed reviews were outmatched by The Big Bang Theory's popularity. The show was a huge hit, with viewers really becoming attached to the misadventures of Sheldon, Leonard, Penny, Raj and Howard. Like Two And A Half Men, it also ran for twelve seasons, closing its run with series finale "The Stockholm Syndrome" in 2019.
They were both sitcom juggernauts, but despite sharing the same creator and some of the same cast, they don't exist in the same universe. In fact, it's been established that The Big Bang Theory is a show within the world of Two And A Half Men, with Jake referencing Sheldon's "Bazinga" catchphrase in one episode while Bertha also mentioned wanting to see the finale of The Big Bang Theory in another.
Charlie Sheen also made a very brief cameo as himself during The Big Bang Theory's season 2 outing "The Griffin Equivalency." While it might have been a ratings success had Charlie and Alan cropped over onto an episode of The Big Bang Theory, it likely would have made for a cringey in-joke too, so it was ultimately for the best the shows had a distinct continuity from one another. While The Big Bang Theory is unlikely to return for a revival season - at least in the immediate future - the franchise has continued in the form of prequel show Young Sheldon - whose fifth season debuts October 2021 - which depicts the childhood of the titular genius.
While The Big Bang Theory lives on in one form, the same can't be said for Two And A Half Men. Sheen's time on the series came to a very messy and public end after being he was fired by CBS for misbehavior, with the actor venting most of his anger on Chuck Lorre. Ashton Kutcher later came on to take his place as new character Walden for the remaining seasons. While a revival with both Sheen and Cryer would probably net big ratings - for the curiosity factor alone - it's feels very unlikely.