Call it the little low-budget pilot that could.

One of the biggest surprises in the 2011-12 season sked announcement from the new regime at NBC was series order for the single-cam comedy “Best Friends Forever,” created by its stars, Lennon Parham and Jessica St. Clair. The project was off the biz’s radar throughout pilot season until just a few days before the Peacock announced its lineup May 16.

But the improv-inspired laffer about the borderline-obsessive friendship between two women caught the fancy of NBC Entertainment chair Robert Greenblatt late in the pilot-screening process.

“We thought at one point that we were caught in an alternate reality where we were dead but no one knows about it,” St. Clair quips.”Best Friends” grew out of Parham and St. Clair’s friendship, which blossomed about eight years ago when both were learning their craft as members of the Upright Citizens Brigade comedy troupe in Gotham. Skein follows the tumult caused when a woman (Parham) decides to live with her boyfriend, only to have her best friend (St. Clair) move in with them after a bitter divorce.

After both made the move to Los Angeles to pursue acting gigs, Parham and St. Clair rekindled their girlfriend bond about three years ago when they decided to write together.

“We speak the same comedy vocabulary,” Parham says.

The project that became “Best Friends” was set up at NBC with the help of another Upright Citizens Brigade alum, screenwriter Scot Armstrong, whose American Work banner has a development deal with NBC. Parham and Lennon wrote the pilot script in a very “Curb Your Enthusiasm” fashion by recording numerous improv sessions and editing the transcriptions.

NBC gave the pair only enough money to shoot a few scenes for a partial presentation pilot — or so the execs figured.

“We were immediately like, ‘Yeah, we can do this,’ ” St. Clair says. “That’s the UCB mentality, you take whatever you’re given and make something out of it.”

The recruited friends and friends of friends, including director Fred Savage, to serve as their creative team and crew.

St. Clair and Parham bought their own wardrobe for the pilot, and they even used most of their own furniture for the sets.

“By the time we were finished there was only a bed left in my apartment,” St. Clair says.The pilot lensed over five days in April on a stage in downtown L.A., followed by one “rogue” day on the streets of Gotham. (“My friend came down to watch us and we were like, ‘Can you hold this light?,’ ” St. Clair notes).

NBC execs were floored when the duo turned in a full-length pilot. Now that they have a six-ep midseason order and a bigger budget, the two still want to keep as much of the indie-movie spirit alive as possible. And they intend to keep harnessing the engine of their own improv, which seems to come best when the two are holed up in a room (to their husbands’ occasional chagrin) for 12 hours a day.

“We’d like to do it as much as possible because that way we’ll keep it close to our voice,” Parham says. “What’s nice is you have a script to work from, but on set we’re always able to create those moments that become our favorites.”