In a parallel universe, Safety Not Guaranteed would get millions of The Big Bang Theory fans to put down their remotes and joysticks to transport into theaters for a sci-fi resonant movie without superheroes. Stars familiar from TV, who have indie cred, may help attract them to a similarly charming story of endearing nerds and the practical companions drawn into their skewed orbit.

Each character feels that their past has put them in a rut into the foreseeable future. Darius (Aubrey Plaza, of NBC’s Parks and Recreation) is first heard rewinding through all that’s gone wrong since her childhood when her mother died, which is probably not the best way to sell yourself at a fast-food job interview. So she’s back living under the roof of her father (Jeff Garlin from HBO’s Curb Your Enthusiasm) and working under the tyranny of bitchy editor Bridget (24’s Mary Lynn Rajskub) at a no pay, no glory Seattle Magazine internship. The debut team of writer Derek Connolly and director Colin Trevorrow met as interns on Saturday Night Live and enjoy biting back about that lowly role in the media world.

Smugly handsome writer Jeff (Jake Johnson, from Fox’s New Girl) volunteers Darius to do the grunt work on his investigative piece, along with a science student branching way out from his comfort zone with this internship, Arnau (Karan Soni, playing an almost identical socially clueless Indian guy as Big Bang’s Raj). They set out for a (cheap) expense-paid road trip up the coast to follow up on a strange help wanted ad (inspired by a real one in a survivalist magazine back in the 1990s). It specifies: “Someone to go back in time with me. This is not a joke. Must bring your own weapons. Safety not guaranteed.” They track down the very earnest inventor who placed the ad, Kenneth (Mark Duplass, the executive producer and also a regular on TV’s The League), and follow him from his crummy day job to mysterious break-ins at labs that put government agents on his trail, too.

But Jeff is really in town to relive his glory days of a summer romance with Liz (Jenica Bergere), who turns out to be refreshingly grounded, so he sends Darius undercover to interview Kenneth. As she passes Kenneth’s arbitrary tryouts to join him in amusing training sessions for their mission impossible, she gains the confidence to discover she’s good at this assignment. Though Jeff’s efforts to educate Arnau in living for today are predictably conventional, the growing relationship between Darius and Kenneth gives the film real heart, especially as she learns more about what drives the man behind the time machine. A sometimes smiling Plaza relaxes her usual one-note deadpan comic persona, while a fast-talking Duplass counters his usual dithering insecurity by playing the zither and singing a lovely song, written by scorer Ryan Miller of the band Guster. Kristen Bell’s cameo, as a puzzle from Kenneth’s past, pleasantly frees her of the cynicism in Showtime’s House of Lies.

While the commingling of romance with science fiction talk recalls the is-he-crazy-or-not? in Brad Anderson’s Happy Accidents (2000), the final transformation seems to be more an updated, scientific take on the lesson Maureen O’Hara learned in the original Miracle on 34th Street (1947), “Faith is believing when common sense tells you not to,” which is how most of us trust in science fiction anyway. (The credits list a “time travel consultant.”) As Darius says, how difficult can time traveling be if both Einstein and David Bowie understand it? Let alone the Big Bang fans, who will enjoy Safety Not Guaranteed.