CBS and Warner Bros. are developing a prequel to “The Big Bang Theory,” according to a report Monday in the Hollywood Reporter. And here’s the twist (because there usually is one): None of the current cast will be involved.

The report is intriguing beyond the obvious simply because a move toward developing a prequel to TV’s top-rated comedy lends a certain element of drama to its future. As THR noted, all the top cast members are in the midst of contract negotiations — a subject that came up at the recent TV critics’ press tour, when CBS Entertainment chief Glenn Geller told writers that he had every expectation of securing the core group for an 11th season and beyond. (“TBBT” just launched its 10th).

Prequels are extremely rare in prime time for all sorts of reasons, but here’s a key one: Why have an ongoing prequel air while the “mother show,” so to speak, is still airing? That could conceivably create confusion — and not just for fans, but for showrunners — and could even diminish the drawing power of the original. TV’s second-most prominent prequel, “Better Call Saul,” launched in 2015, or two years after the end of “Breaking Bad.”

There is certainly an exception to this rule — notably TV’s most prominent prequel, “Fear the Walking Dead,” which has done well for AMC and of course takes place just at the outset of the walker outbreak. “The Walking Dead” remains television’s top-rated series among young adults. So no harm, no foul there.

Nevertheless, “Fear” isn’t as much a “prequel” as simply a corresponding series that just happens to unfold in the same fictional universe. So could the prequel development of “The Big Bang Theory” suggest that CBS is looking to the day when “TBBT” goes the way of “Seinfeld,” “Friends” and other tent-poles of yore — most of which rarely last beyond a decade because costs become so prohibitive?

Or is CBS simply looking to build out the franchise, with something so different that no one will mind — least of all fans?

There’s already a great deal known about Sheldon Cooper’s (Jim Parsons) past — that he was raised in Texas, had a close relationship with his grandfather (“Pop-pop”), and was a child prodigy. A series like this — which THR described as “single camera” and similar to “Malcolm in the Middle” — would appear to have plenty of back story to develop.

THR also reported that the cast members — Parsons, Johnny Galecki (Leonard), Kaley Cuoco (Penny), Simon Helberg (Howard), Kunal Nayyar (Raj), Mayim Bialik (Amy) and Melissa Rauch (Bernadette) — are seeking “raises” beyond the “historic deal” reached two years ago with each.

A CBS spokesman declined to comment.