Bun in the oven: A half-baked idea?

There's a visible baby bump on the set of "How I Met Your Mother," but no one's paying it much attention.

In a flashback scene for an upcoming episode, the ever-present narrator's memory is lapsing and he can't recall whether Lily (Alyson Hannigan) was pregnant during the moment he's recounting. As Lily spars with Barney (Neil Patrick Harris), her burgeoning belly remains unmentioned, serving simply as a resting spot for a plate of Chinese food.

Now in its sixth season, the show is toying with the idea of employing a device much belabored in sitcom land: the addition of a baby.

A due date is still unknown - and for some fans, that's OK. Much of the appeal of the CBS sitcom has centered on the interminable mystery of whom Ted Mosby (Josh Radnor) will ultimately marry. But suspense can hold viewers' interest for only so long before it grows frustrating.

Baby talk has loomed over the series for a while, with longtime couple Lily and Marshall (Jason Segel) flirting with parenthood this season. Even if the stork doesn't drop by this season, it's fated to happen.

"I think we'd be super cute with a baby," Segel said during a set break. Still, the show's producers are proceeding with caution.

"There's fear: Will it limit us? Will the show lose something?" admitted executive producer Craig Thomas. Of course, there's that teeny tiny issue: In prime time, infants have a mixed record.

Some lamented that Murphy Brown lost her snarky edge after she gave birth at the end of the show's fourth season. Others found that "Mad About You" got only more maddening after married couple Paul and Jamie welcomed a daughter near the end of the show's run. Then there was "Roseanne," which decided to add a fourth kid - named Jerry Garcia - to the household in its seventh season.

"I think it's thought of as a potential death knell to a show," Thomas said. "But at the same time, the series is all about growing up, so to not address it, to not see this couple who has been together since age 18 get to that point would seem dishonest."

"How I Met Your Mother" isn't alone in its baby quest. Scour the TV landscape and peewee youngsters are rampant. A little tyke was recently added to NBC's "The Office," shortly after Jim and Pam completed another TV convention - getting married. "Dexter's" bundle of joy came in the form of baby Harrison, while another Showtime series, "Weeds," shows Nancy trying to protect her newborn from his drug lord father. Fox's "Raising Hope" centers on a cherub-faced bambino.

CBS comedy "Rules of Engagement," now in its fifth season, is also feeling a bit fertile, with Jeff and Audrey Bingham (played by Patrick Warburton and Megyn Price) looking to conceive via a surrogate. At first, the storyline concerned Price.

"She was worried it might ruin the show," said creator Tom Hertz, who later added, "I looked back at every episode we've done and asked whether there were any episodes we couldn't have done with an unseen baby in the second bedroom. And there was barely any... The entire series doesn't have to suddenly stop because there's a baby - that happens in real life, not TV."

Sometimes, the kid is added to liven up an aging cast. Angel Cohn, managing editor of the blog Television Without Pity, cited Seven ("Married With Children") and Emma ("Friends") as examples. But often the child gets lost in the shuffle. And there are inherent problems with baby characters, as when they age rapidly over a short span of time, while other family members don't (in "The Fresh Prince of Bel-Air," Little Nicky aged from a baby to a preschooler in a matter of months).

"For it to work, it has to make sense," said TV historian Tim Brooks.