Lila likes singing along to songs in the car—any song, with as much feeling as is inhumanly possible. She gets seasick, so Eddie's fishing plans are out. So are his dreams to ride a burro through Mexico, because she thinks it's dangerous. Even though she wanted to save sex for later in their relationship, she turns out to be a wildebeest in the sack and doesn't know the definition of "missionary position." She spots an old couple at a diner (she has to hold hands while eating) and says that will be her and Eddie in ten years, so math isn't her strong suit. And that deviated septum? Cocaine. All of this is piled on so quickly, it's no wonder Eddie begins to have doubts about his marriage before their first fight. The material here is genuinely funny in a nightmarish sort of way, and it's only the beginning of the discoveries Eddie makes on his honeymoon. The comedy works in this section, and Ben Stiller and Malin Akerman play the sap and the nut-job without overdoing it.

The movie starts to wobble with the introduction of Miranda (Michelle Monaghan), who's at the resort to celebrate her aunt and uncle's anniversary with her family. Miranda is everything Eddie thinks he wants in a woman, and he does a fine job of avoiding telling her that he happens to be on his honeymoon. Eddie goes from likeable dope to pathological liar, and the script sets in motion a chain of misunderstandings to accompany his lies so that, at one point, Miranda and her family are convinced Eddie is a widower, his wife murdered by an ice pick-wielding maniac. It's too much convenience and too many hateful traits tacked on to Eddie for any of it to work. Topping the whole extreme mix-up is a pileup of recurring and set-up jokes in an elaborate but energy-less climax that involves a mariachi band, a hot pepper in the nose, a chunk of meat out a different nose, a fall into the ocean, a jellyfish, and the only known comic remedy for its sting. That the movie doesn't end there is a further fault, and soon Eddie is involved with illegal immigrants and turns into a legitimate nutcase himself.

It's almost enough to make one forget how promising The Heartbreak Kid started but ultimately only serves as disappointment for the promise wasted on the obvious and occasionally disturbing. When the final scene comes with repeating caddish behavior from Eddie, we don't know whether to laugh or slap our foreheads. Or maybe him.