Mark Duplass isn’t your typical mad scientist, but then Safety Not Guaranteed isn’t your typical sci-fi flick. 
Colin Trevorrow’s quirky, low-key film is less concerned with the history-changing possibilities of time travel than the human-level emotions that drive the desire to turn back the clock. Duplass’ eccentric loner Kenneth claims to have a time machine at the ready, but isn’t planning to assassinate Hitler or run with T-Rexes; he simply wants to revisit the day he blames for his own downfall. He places a classified ad (based on a real-life ad that instigated a brief Internet phenomenon) that’s discovered by a magazine reporter (Jake M. Johnson), who sees an easy subject for a mocking article.
Intern Darius (Aubrey Plaza) tags along, though her above-it-all cynicism soon begins to peel away as she falls for Kenneth and uncovers her own emotional scars. Plaza has been practicing her sarcastic charm on Parks and Recreation and she essentially plays a more emotionally resonant spin on that character here, while Duplass strikes the perfect balance between obsessed wacko and wounded soul — especially as some of his paranoia begins to seem justified. Their relationship, more than the mystery of whether Kenneth can back up his time-travel claims, forms the core of the film, though even Johnson’s slimy reporter reveals a desire to return to the past. In his case, it’s through a reunion with a former flame who turns out to be his ulterior motive for pursuing the story, but his pursuit of nostalgia is not far removed from Kenneth’s more fantastical mission.
Ultimately, Johnson’s subplot feels half-hearted, and the stereotype-bending central characters are surrounded by actual, lazy stereotypes: Darius’ fellow intern is a nerdy Indian-American, while Johnson’s ex is a “real woman” who challenges his shallow assumptions. Trevorrow dials back his story’s grander implications a bit too much; by the time Kenneth unveils his time machine, neither the ending of the time machine working or it not working would be particularly satisfying, and the questions left unanswered aren’t compensated for by the offbeat but slight romance.
