CULVER CITY, Calif. -- Since he became the showrunner of "Cougar Town" last spring, Ric Swartzlander does not often use his personal office at that comedy's bungalow headquarters here, preferring to work alongside his colleagues in a shared writers' room.
A visit to Mr. Swartzlander's office in the fall suggested reasons he avoids it: Its thin walls do not suppress the sounds of laughter (or singing) from other rooms; it is a frequently traveled path to a bathroom; and it is sparsely decorated, with few adornments other than a jar of pens and pencils left over from a previous regime.
"I ought to get rid of it," he said. "At the very least send the glass off to be washed."
Yet for Mr. Swartzlander these inconveniences are more than fair trade for the top creative post at "Cougar Town," which on Tuesday began its fourth season, after moving from ABC to uncertain basic-cable turf on TBS.
And while he arrives with the endorsement of the show's creators, Bill Lawrence and Kevin Biegel, Mr. Swartzlander's ideal situation at "Cougar Town," an ensemble comedy about a divorcee (Courteney Cox) and her wine-sipping friends, is one in which no one notices his predecessors have left.
"I don't care if anybody ever knows my name," said Mr. Swartzlander, whose credits include unlamented comedies like "Samantha Who?" and "Man Up."
"Honestly the thing that worries me is whether or not anybody knows the difference -- that it's as consistent as the show has always been."
These same circumstances are being repeated at several established series across the broadcast and cable networks, where their showrunners -- the people in charge of hiring, firing, budgeting, overseeing the writing and making the significant creative decisions -- are leaving, sometimes by choice and sometimes not.
To their successors they bequeath popular programs with spelled-out rules, characters and formats -- and often the understanding that their shows should continue to operate as if no change in leadership had occurred.
The incoming showrunners accept such seemingly restrictive conditions, usually hoping that the success of their inherited series rubs off on their own resumes.
But these days new showrunners face more scrutiny and pressure than ever, from savvy audiences that have become increasingly connected to the creators and producers of their favorite shows and who interpret these behind-the-scenes transitions as omens of doom.
"The reality of what we've stepped into we could not be prepared for," said Moses Port, who took over as a showrunner of the NBC comedy "Community" with his writing partner, David Guarascio, in May. "The rabid fans, you don't know how rabid they are until you step into it."
Mr. Guarascio and Mr. Port, who have written, produced and consulted on shows such as "Happy Endings" and "Mad About You," were vilified by part of the "Community" fan base when they took over from that comedy's creator, Dan Harmon.
(Writing on his blog after he was let go by Sony Pictures Television, the studio that produces "Community," Mr. Harmon said, "I'm not saying you can't make a good version of 'Community' without me, but I am definitely saying that you can't make my version of it unless I have the option of saying, 'it has to be like this or I quit' roughly eight times a day.")
Mr. Guarascio said he and Mr. Port faced "massive hesitation" about replacing Mr. Harmon at "Community," a show about a group of misfit students at a community college.
On the one hand, Mr. Guarascio said, the "hard part" of the show was done: "Dan really set down the rules for this universe, and everyone else has put their blood, sweat and tears into the show," he said. On the other hand, the show's devotees "are very protective," he said, "and you want to do right by them."
"It's like, 'Who are these new guys coming in?' " Mr. Guarascio said. "Wait, we're the new guys."
"Community," which has built a loyal following but has struggled in the ratings over its first three seasons, may be the most notorious case this season of a series changing showrunners midstream, but it is hardly the only example. When "Smash," the NBC comedy-drama about the making of a Broadway musical, returns in February, it will have replaced its creator, Theresa Rebeck, with Joshua Safran, a former producer of "Gossip Girl." He is adding several characters, excising others and introducing new plotlines.
The NBC comedy "Whitney" changed showrunners between its first and second seasons, and a similar switch is happening at that network's "Up All Night," whose creator is leaving, and which is moving from a single-camera to a multicamera format and adding a live audience.
Elsewhere, the cable channel AMC has announced a change in showrunners for a coming third season of its historical drama "Hell on Wheels." And when it ordered a fourth season of its hit zombie-apocalypse thriller, "The Walking Dead," in December, AMC said it was parting ways with the showrunner Glen Mazzara, who had taken over from the original showrunner, Frank Darabont. (AMC said the network and Mr. Mazzara had "a difference of opinion about where the show should go moving forward"; Mr. Mazzara said simply that he had "told the stories I wanted to tell and connected with our fans on a level that I never imagined.")
Ken Levine, who, with his writing partner, David Isaacs, was a head writer on "M• A• S• H" and a creator and showrunner of several other comedies, said these kinds of transitions were not unusual in television and not necessarily bad signs for the health of a show.
Mr. Levine said that showrunners leave because they want to pursue other projects or they become burned out by the demanding job.
Citing a line he attributed to the "Happy Days" creator Garry Marshall, Mr. Levine said: "What good is all the money? You can't spend it at Cedars" -- that is, the Cedars-Sinai Medical Center in Los Angeles.
What has changed over the years, Mr. Levine said, is that television viewers have become increasingly knowledgeable about the creators and producers of their favorite shows, from Steven Bochco (who helped create "Hill Street Blues," "L.A. Law" and "NYPD Blue") to David Chase (at HBO's "Sopranos") to Matthew Weiner (at AMC's "Mad Men").
Before he was offered the job of "Cougar Town" showrunner, Mr. Swartzlander said, he had seen only a few episodes of the series. He was divorcing his wife and helping to raise their teenage daughters and not necessarily interested in the demands of being in charge of a series.
But after catching up with "Cougar Town" in weekend-long cram sessions, he said, he was ready to put his nose back to the grindstone and help execute other people's creative visions.
"I know what my job is supposed to be, which is delivering Bill and Courteney and TBS what they want," Mr. Swartzlander said. With a laugh, he added, "Going through a divorce, it's really hard to hurt my feelings now."