That's a real problem, since the central trick is — well, what follows is a spoiler the distributor would prefer we not spill. The film presents each member of its lead couple with an idealized, possibly magical version of the other. The gag is that in a country house prescribed them by their therapist (Ted Danson), she meets the him she's always wanted — he does sit-ups! And vice versa — she lets him eat bacon! But sit-ups and bacon aren't just amusing, incidental details I've selected from a pile; they're almost the full extent of what the filmmakers have come up with to distinguish the dream mates from the real ones. Moss' and Duplass' best moments come when their confused characters (Ethan and Sophie) first work out that something strange is going on and then decide to roll with it.
Sophie crinkles up with brittle glee but she's also the power in the relationship, using that glee to nudge Ethan along. Scenes with the improved better halves, meanwhile, rarely spark, and often kick off like improv exercises: Two actors standing there, grinning, waiting to see what the other's going to do. Some of the surprise works, but the final gotcha won't getcha.