A lot of comedy and drama relies on poor communication. It dates back to the old “Who’s On First” joke from Abbott and Costello.

“Our Mrs. Reynolds” starts out with the classic marriage misunderstanding. While staying on a planet called Triumph, Captain Mal receives a flower crown and shares a dance with a local girl named Saffron only to find out later that he participated in a marriage ceremony. (You wanna know why it takes Catholics long to get married? To prevent stuff like this from happening!)
Having Saffron on board brings up different stuff from the members of the crew. Zoe and Wash debate on Saffron’s traditional beliefs on what a wife should be and whether or not Wash is jealous of Mal having a submissive wife. Jayne wants to trade his best gun just to jump Saffron’s bones. Book warns Mal that taking advantage of Saffron will send him to “special hell.” Inara snarks at Mal, hiding her jealousy. Kaylee thinks it’s all sweet. Simon and River don’t really do much in this episode.
Of course, later on, it’s revealed that Saffron is not who she says she is. She seduces Mal enough to give him a literal knockout kiss. She tries to do the same to Wash, but decides on punching his lights out instead when he refuses. Then, she tries to seduce Inara to no avail. Inara tries to come to Mal’s rescue and kisses him, only to realize that he was just unconscious before succumbing to the effects of the drugged lipstick herself.
Saffron gets to work damaging the ship’s navigational system and sending Serenity into an electromagnetic net set up by scavengers who want to take the ship apart and sell off the pieces for easy money. Thankfully, the crew of Serenity is able to repair the damage and disables the net with the help of Vera (Jayne’s favorite gun). Mal finds Saffron on some distant snowy planet where the two of them debate on her motives. Then Mal knocks Saffron out and recovers the shuttle she stole.
The episode ends with Mal in Inara’s shuttle, in which Mal tells Inara that she couldn’t have just tripped like she claimed, but thinks that she kissed Saffron instead. Inara and the audience are left dumbfounded and every Mal/Inara shipper goes: SHE KISSED YOU, YOU MORON!
The reason that Saffron’s plan worked so well is because she’s a practiced liar and relied on everyone’s preconceptions of what women from backwater planets were like. Also, nobody thought to ask why, if she claimed to be married to Mal and thought that he knew of the marriage, did she feel the need to sneak aboard the ship. She also had a story prepared, calculated to seduce her targets. She took advantage of Mal’s ignorance of the Bible and quoted something not actually in the Bible. (If it was me, she would be misquoting Song of Solomon, but I digress.) She has a myth of Earth-that-Was that focused on the sky in the hopes of seducing Wash. She used Inara’s status as a Companion and the fact that Companions sometimes have female clients in an attempt to seduce her as well.
But of course, liars can only hold out for so long before they get caught. And in the end, the reason that the crew of Serenity lives to see another day is because they trust each other. Now if only Mal and Inara could learn some things about communicating their feelings for each other.