It’s a very merry and manic post-apocalypse during a first Christmas for Fox’s ‘Last Man on Earth’

Christmas and the post-apocalypse: They just go together.

Or at least they do in the off-kilter world of the Fox comedy “Last Man on Earth,” in which former “Saturday Night Live” star Will Forte plays a tetchy omega man presiding over a crew of misfits in Tucson during the End Times, after disease has wiped the planet of all but a few survivors.

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It’s an unlikely premise for a network comedy, as Forte, the creator and executive producer, freely admits. But as the gang shot a special “Secret Santa” episode a few weeks ago at a studio in Chatsworth — the resulting installment airs Sunday night — it was clear that “Last Man” has evolved into an ensemble family, one that costar Mary Steenburgen compares to “Cheers,” where her husband, Ted Danson, led the cast.

Except that “Last Man” is more like “Cheers” darkened with helpings of “The Walking Dead” and “The Leftovers.” In his review of the first two episodes last spring, Times critic Robert Lloyd called “Last Man” “a comedy about existential cares and social mores in the absence of society.”

The show springs from the manic intensity of Forte, who spends so much time at the set he was crashing at a nearby Radisson until he finally broke down and rented an apartment two blocks away.

“I never thought anything would be harder than ‘SNL,’” Forte, 45, said as crew members with headsets buzzed by on a set designed to look like a living room dripping with Christmas decor. “That was such a pressure-packed job. But it was nothing compared to this. Part of it is my own fault. I’m a control freak.”

Perhaps fittingly, he has taken on the physical appearance of a slightly demented mountain man for the series, à la his character Falconer on “SNL,” where Forte appeared for eight seasons ending in 2010. There he developed offbeat audience favorites such as Greg Stink, a clueless sportscaster, and MacGruber, a would-be action hero who can’t stop chattering at climatic moments. Then, in 2013, he won acclaim as the adult son struggling with his elderly father’s physical and mental decline in the dark comedy “Nebraska.”

“Last Man” grew out of Forte’s writing sessions with the creative team of Phil Lord and Christopher Miller, best-known for the “21 Jump Street” movies. At some point Lord and Miller had scribbled down an idea for an end-of-the-world comedy. The idea was dropped, and they kept brainstorming.

But “as Chris was grabbing his jacket to leave to go some family dinner, I don’t know, maybe the notebook was open to that page and we looked at it and said, ‘What about this ‘last man on earth’ idea?’ ” Forte recalled.

On “Last Man,” Forte’s Phil Tandy is an oversensitive basket-case with a face framed by an unruly beard of epic proportions that has grown into one of the show’s leitmotifs. Forte conceded that the wiry shrub on his cheeks doesn’t make for easy living off-camera — “it’s gross and filled with bacteria,” he said — but it was important to him to grow the facial hair and not rely on makeup and spirit gum.

Sunday’s episode concerns a gift exchange organized by Carol, the eccentric, chipper woman who married Phil in the pilot episode. She’s played by Kristen Schaal, best-known for her work on “The Daily Show” and “Bob’s Burgers.” The holiday occasion gives the writers the opportunity to tap the weird group dynamics that lie beneath the surface.

Tandy, for example, was really hoping that the discovery of female survivors— including blonde temptress Melissa (January Jones, late of “Mad Men”) — would enable him to cultivate a kind of harem. But that was complicated by the arrival of another, much hunkier Phil (Boris Kodjoe), not to mention Todd (Mel Rodriguez), a shy and sweet-natured man who proves more of a draw for the women.

“We could all be lying,” Steenburgen, a veteran star whose resume includes “Justified” and “Orange Is the New Black,” said during a break in shooting. She plays Gail, a mysterious woman who was married before the virus outbreak but whom Phil found traveling with a much younger woman, Erica (Cleopatra Coleman). “My whole backstory could be a lie.”

Carol is beside herself with excitement when her secret Santa gives her the notorious green Versace dress that Jennifer Lopez wore to the Grammys in 2000. It’s after the apocalypse, you see, and such objects are lying around for the taking.

Schaal says that such flights of fancy aside, “Last Man” offers a more realistic take on what life might be after the apocalypse than does, say, “Walking Dead.”

“There’s not a lot of opportunity to play with different quirks and stuff when you’ve got to survive and kill zombies,” Schaal said. “This is just like taking a slice-of-life, moments in that world, and how people are going to react and how personalities are going to come through.”

Jones, who came from the highly scripted world of “Mad Men,” appreciates the looser style of working. “I like having the freedom to do improv and the creative freedom we have with dialogue,” she said during a break on set.

That loose style of humor is now helping Fox achieve a long-elusive goal: finding a live-action companion to its Sunday-night animation lineup, led by “The Simpsons.”

For this season so far, “Last Man” is averaging a modest 2.9 million total viewers in same-day viewers, according to Nielsen. But that number jumps to 6.6 million over a monthlong period, which includes streaming on Hulu and the Fox Now platforms.

Fox chief Dana Walden said the show is doing a good job connecting with elusive younger viewers, especially men.

“It’s been challenging over time at the Fox network to find live-action comedies that totally fit with in with our hugely successful animated shows, and ‘Last Man on Earth’ is a show that feels exactly right for the audience,” Walden said.

She’s not surprised by Forte’s intensity.

“People that have worked with him on ‘SNL’ say this is a guy who commits. His work is really important to him, he takes it really seriously,” Walden said. “He was the person on ‘SNL,’ if you talked to some of the writers that worked with him, that they were so happy if he ended up in one of your sketches because he would just go for it.”

And that’s the case on “Last Man,” even if the result has had a near-apocalyptic outcome on his free time.

“I just wish that there was a lot more time to see friends and family and stuff like that,” Forte said before heading back to work. “It’s just — I still haven’t figured out that magic formula of working and still having that time.”

He sighed. “My friends and family have been very patient with me,” he said.

Twitter: @scottcollinsLAT