The two comedians play il lungo/the long (Ciccio) and il corto/the short (Franco), in reference to their heights, their character names and their own otherwise interchangeable as usual. They are the long suffering-servants to a countess, who is devoted to il gatto/the cat, Archibaldo, in the way that only rich old ladies in movies can be.
An image from the cartoon credits
The thing that keeps the two idiots there, with Ciccio the smarter, again as always, is the promise of a pay-off when the countess snuffs it.
This soon happens, as she discovers that her purportedly faithful Archibaldo has not been as faithful as she had believed – he is a tom cat, after all, and will do what tom cats do, namely fathering kittens.
Franco duly engages in a spaghetti western style showdown with Archibaldo, cued with appropriate music and with Ciccio serving as referee. The outcomes is predictable, as Franco boots the cat out of the house. We need not be overly concerned for the animal's welfare, however, given the comedy context - you are not about to see a beloved comedian actually kick a real life cat - and the necessity for a dramatic complication that will prevent our two heroes from enjoying their just reward (or desserts) just yet.
This comes in the form of the reading of the Countess's will, which promises Franco and Ciccio some money, but only on the condition that they continue to take care of Archibaldo. (Most of the estate goes to the cat protection charity.)
No problem, they think: one cat is surely as good as another. Unfortunately the Countess had Archibaldo photographed and fingerprinted, making for one of the film's more inspired gags.
Franco and Ciccio thus begin a desperate search for Archibaldo, il gatto. At this point the film veers into Eurospy territory as they become mixed up in the attempts of Interpol and the Secret Service to apprehend a master-criminal (Ivano Staccioli) also known as The Cat...
This is one of those films that defies criticism. As a Franco and Ciccio vehicle it's no better or worse than the four or five other examples of their mainstream work I've seen: Funny in places, but something that's never likely to be respectable in the manner of a Toto or Tati. Fulci, meanwhile, does what he's there to do, namely letting the two comedians do their stuff. What's perhaps lacking, excepting the slides of Archibaldo as an image that would recur in his gialli a few years later, is the sense of a developing personality and style.