Comedy is funniest when the characters are trying their damnedest to not be funny. Roger Ebert writes, "A person who wears a funny hat isn't funny -- but a person who doesn't know he's wearing a funny hat? Ah, now that's funny." A Fish Called Wanda takes this to the extreme -- the characters can all see each other's funny hats, but they are unable to recognize their own gross, eccentric faults.
The story begins with a jewel heist that ends in betrayal. Wanda (Jamie Lee Curtis) and Otto (Kevin Kline) are lovers who pretend to be siblings so that they can swipe the jewels from stuttering Ken (Michael Palin) and George (Tom Georgeson), whom Otto and Wanda secretly ratted out to the police. George is defended in court by Archie Leach (John Cleese), a stuffy barrister whom Wanda resolves to seduce so that she can find out where George has hidden the jewels.
One of the funniest things the movie deals with is the stubbornness and hypocrisy of the principal players. For example, the imprisoned George orders Ken to kill an old lady who identified George after he almost ran her over while escaping from the heist. Ken does a poor job of killing the old woman -- in fact, there is some unfortunate collateral damage done that especially horrifies him. His scenes of mourning are hysterical, moreso when compared to a scene near the end of the movie with Ken and Otto.
Speaking of Otto, he provides some of the biggest laughs in the movie -- Kline didn't win that Best Supporting Actor Oscar for nothing. One of Otto's funniest attributes is how he constantly bemoans the pretentious, holier-than-thou attitude of the English while simultaneously quoting Nietzsche and warping Buddhist belief to the point where he uses meditation to channel his aggression so that he will have an easier time of killing people. Any time Otto tries to reconcile his "intellectual" bent with his tendency to fly off in the lowest, most vulgar temper tantrums, the scene is a winner.
Another thing that is great about the movie is how it plays with the stereotypes the Americans and the British have of each other, especially in Otto's interactions with Archie. Otto is a total stereotype -- he thinks he's clever, but he really isn't, and he's constantly whining about a perceived arrogance in the British. He also swears a lot. Archie, on the other hand, is insufferably introverted and perpetually mortified at everything going on around him. He has a withering comment ready for every situation, but he is dominated by his most shameful instincts. And, of course, these two interact a lot. Coarse Americans + refined Englishmen = hilarity.
One of the classic comedy devices is men who think they are in control at all times, until a woman comes along who wraps them around her finger. Curtis is amazingly sexy as Wanda, and that sexiness is used to its full advantage for hilarity. It's wonderful to see her immediately change from the innocent, wide-eyed persona she uses to charm Archie to her normal, tough and straightforward personality in front of Otto, because, dumb as he is, he can't see that she's been pulling the same act on him the entire time.
Of course, as a British character in a British comedy, Archie has absolutely no chance of escaping the most horrifying embarrassments imaginable, and the movie throws plenty at him. I won't spoil them because they deserve to be surprises; however, I will say that if you suspect there is no way Archie can not get caught canoodling with Wanda, then your suspicions are correct. Watching Archie try to worm his way out of the most disastrous situations is a joy to see.
Something that seems to be underrated in comedies, especially in recent years, is a good story. There are so many moviemakers who seem to believe that they can just throw whatever they feel like onscreen with the thinnest of plots to support it, and it will be a work of genius. It takes a hell of a comedy to survive with little to no plot to support it, and, sorry, but Epic Movie isn't it. A Fish Called Wanda supplies a genuinely interesting caper story filled with great double- and triple-crosses that strengthens the laughs while also not bogging down the movie with clumsy plotting. It successfully combines a great story with great laughs, which is definitely not easy to do.
If you like to laugh at all, then watch A Fish Called Wanda. That's all I can say.
EDIT: More retroactive scene additions! YouTube flags this as not being appropriate for minors, but personally I don't think it's objectionable at all because it's so damned silly. Anyway, in this scene from A Fish Called Wanda, Otto gets in a fight with Wanda and then gets her going by speaking Italian.
