The humor in this period kung fu comedy (which appears to have its origins in Peking Opera) may be too Chinese for some Western viewers to grasp, but it has other rewards and is certainly an interesting addition to director Lau Kar-leung's filmography. Mortal enemies "Rat" Bai Yu-tang (Alexander Fu Sheng) and "Cat" Jien Chiu (Adam Cheng Siu-chau) are engaged in a prolonged battle to determine who is the superior swordsman. After numerous skirmishes, they consult their master (a beard-stroking Lau Kar-wing), who, much to their dismay, announces that they are both equal in ability. The old man gives Bai his "Nine Ring Sword" which allows him to defeat his opponent. Not one to show favoritism, the master proceeds to give Jien a spear that will counter the sword and he emerges victorious over Bai in a re-match. Their next bout ends in yet another draw but concludes with the two families beating each other up! Jien and his sister (Kara Hui Ying-hung) encounter Emperor Yung Hsi (Gordon Lau Kar-fai) when they inadvertently rescue him from thieves out to grab his invaluable jade seal. The emperor (who believes himself to be a kung fu master but cannot even perform the most basic moves) rewards Jien by making him a royal guard. Infuriated, Bai vows to steal the jade seal but is framed by his cohorts and left behind to be captured. Accepting Jien's plea for leniency, Yung gives Jien and Bai one day to find and return the royal insignia.

There are outstanding acrobatics throughout and the heroes' climactic battle against the traitorous "rats" (including Johnny Wang Lung-wei and Chang Chan-peng), who attack from under the water, beneath the ground, and through walls, is delightful fun. The entire film flows with the grace and precision of a play that the stars have been performing in for years, and their energy and enthusiasm are well communicated to the viewer. CAT VS RAT is definitely not for all tastes (it is certainly understandable why Shaw Brothers did not create an English-dubbed version for export), but its energy, overstated (but winning) performances, and the amazing dexterity on display make it difficult to resist. Hsiao Hou and Wilson Tong Wai-shing also appear. The film was re-made as the 2003 Lunar New Year attraction CAT AND MOUSE,
with Andy Lau Tak-wah and Cecilia Cheung Pak-chi in the respective roles.