Given all the musicals we've seen on TV recently -- NBC's live-performance versions of "Peter Pan" and "The Sound of Music," not to mention ABC's "Galavant" and all six seasons of Fox's "Glee" -- it's a wonder that the pipeline hasn't flowed in the opposite direction, from the small screen to Broadway.

That may change with the announcements that a couple of TV-based musicals are in the works. One is "Bombshell," the Marilyn Monroe biographical musical that was created and staged over the course of two seasons on NBC's "Smash." Bringing it to Broadway would seem easy enough -- the songs and choreography already exist; all that's needed is a book.

The other is a stage version of "Downton Abbey," which may launch after the British drama's sixth and final season wraps this winter. John Lunn, who composes the music for the series, says he envisions an international tour, starring the TV cast and writer/creator Julian Fellowes as a narrator, along with some period music you might hear on the Crawleys' gramophones (Elgar, 1920s jazz).

Are these even aa good idea? "Smash" wasn't exactly a hit series (it ran from 2012-13), so it's not clear that there's much of a market for a "Smash"-derived musical. On the other hand, the songs were more popular than the show, and anything with Monroe's name in it ought to be a big seller.

The "Downton" show doesn't sound much more promising, though anyone who watched their hilarious guest spots on "Galavant" knows that Hugh Bonneville (Lord Grantham) and Sophie McShera (kitchen maid Daisy) can sing. Elizabeth McGovern (Lady Cora) has fronted her own rock band, Sadie and the Hotheads. Who knows if Maggie Smith can sing or dance, but who wouldn't pay money to see her try?

Still, the fact that these TV series are even being pondered as possible stage musicals probably says more about the current desperation of Broadway than it does about TV. After all, Broadway commonly adapts books, movies, straight plays, pop stars' back catalogs, and even comic books into musicals, yet TV adaptations are as rare on Broadway as belters whose voices can reach the back row without body mics.

Among the handful of TV series that have made it to the stage is "The Addams Family" (the 2010 Broadway musical purports to be based on the Charles Addams cartoons that were also the inspiration for the 1960s sitcom, but it's clear that the characterizations owe pretty much everything to the TV show and the movies it spawned). Some British shows have been adapted as straight plays, including "Yes, Prime Minister" and "Doctor Who" (which has spawned at least three plays over the past 50 years).

Back in 1992, Jill Soloway mounted a touring production called "The Real Live Brady Bunch," which staged tongue-in-cheek performances of individual "Brady Bunch" episodes. Soloway would go on to become a top TV writer/producer herself ("Six Feet Under," "Transparent"). The show featured Melanie Hutsell as Jan Brady (a character she would reprise on TV after she joined the cast of "Saturday Night Live") and, as Mike and Carol Brady, a pre-fame Andy Richter ("Conan") and Jane Lynch ("Glee"). Speaking of "Glee," back when the "Glee" cast first went on a concert tour five years ago, there was a rumor that the show's creators were developing a stage musical version as well, but it never happened. But the two tours at least featured the TV cast performing in character.

It's clear why TV hasn't been a wellspring for stage adaptations: it's hard to cram a lengthy TV series into a 2 1/2- hour show. And there may be a psychological barrier, for both producers and audiences, in coming to terms with an expensive stage adaptation of something you can watch every night for free (or almost free), in syndicated reruns or binge-watched as part of your streaming subscription.

Nonetheless, it seems like more TV-to-Broadway adaptations are inevitable. Not only is Broadway always hungry for new material with brand recognition, but it's also spent the last decade or so getting a number of its most popular performers from TV. "American Idol," in particular, has been a strong source of Broadway talent, with the likes of Fantasia Barrino, Clay Aiken, Jordin Sparks, Justin Guarini, Frenchie Davis, Constantine Maroulis, Taylor Hicks, Ace Young, Diana DeGarmo, Syesha Mercado, and Crystal Bowersox all using their Fox-bred fame to sell musical theater tickets. "The Voice" Season 6 winner Josh Kaufman went straight to the Broadway musical stage last year, starring in a revival of "Pippin."

With TV creating the next generation of Broadway musical stars, it seems it's only a matter of time before the medium generates the shows themselves. The secret seems to be using shows that can be spun off into self-contained stories. Shorn of "Smash"'s backstage drama about its creation, "Bombshell" works in that respect, "Downton Abbey," which has always been more about character interaction than plot, could also come up with a brief storyline that doesn't require a lot of character evolution or elaborate plot developments. And there's no reason a musical couldn't use the "Doctor Who" or "Brady Bunch" model and offer just a single episodic story from the show's familiar lore.

A stage adaptation of "Glee" or "Galavant" could certainly work, though it's likely that more nostalgia-minded titles would sell more tickets. Imagine a musical version of "Frasier," a show that often borrowed from the structure and timing of door-slamming stage farce. And if "Doctor Who" works, why not "Star Trek: The Musical"? Now that "Seinfeld" is all over Hulu, why not Broadway? They could serve Junior Mints and slices of marble rye at intermission. (But not Pez.) It's Tony gold, Jerry, Tony gold!