Domestic kittens in developed societies are usually vaccinated against common illnesses from two to three months of age. The usual combination vaccination protects against feline viral rhinotracheitis (FVR), feline calicivirus (C), and feline panleukopenia (P). This FVRCP inoculation is usually given at eight, twelve, and sixteen weeks, and an inoculation against rabies may be given at sixteen weeks. Kittens are usually spayed or neutered at seven months of age, but kittens may be neutered as young as seven weeks (if large enough), especially in animal shelters.[20] Such early neutering does not appear to have any long-term health risks to cats, and may even be beneficial in male cats.[21] Kittens are commonly wormed against roundworms from about four weeks.[22]
Purring may have developed as an evolutionary advantage as a signalling mechanism of reassurance between mother cats and nursing kittens. Post-nursing cats often purr as a sign of contentment: when being petted, becoming relaxed,[143][144] or eating. The mechanism by which cats purr is elusive. The cat has no unique anatomical feature that is clearly responsible for the sound.[145] It was until recent times,[when?] believed that only the cats of the Felis genus could purr. However, felids of the genus Panthera (tiger, lion, jaguar, and leopard) also produce non-continuous sounds, called chuffs, similar to purring, but only when exhaling.[146]

Clio Yun-su Davis is a game designer and writer who creates larps, tabletop roleplaying games, interactive fiction games, and card games. Their freeform game The Long Drive Back from Busan won the Golden Cobra Challenge award for Best Game That Incorporates Meaningful, Non-Romantic Relationships in 2017, and their game about the future of ancestor worship, The Truth About Eternity, was presented at Fastaval 2019 in Denmark. 
Cats conserve heat by reducing the flow of blood to their skin and lose heat by evaporation through their mouths. Cats have minimal ability to sweat, with glands located primarily in their paw pads,[105] and pant for heat relief only at very high temperatures[106] (but may also pant when stressed). A cat's body temperature does not vary throughout the day; this is part of cats' general lack of circadian rhythms and may reflect their tendency to be active both during the day and at night.[107]:1
Additionally, Cats was the first Broadway and West End show to capitalise on merchandising as a major revenue stream. Stalls were set up in the theatre lobbies to sell souvenirs ranging from toys and watches to coffee mugs, all of which were emblazoned with the cat's-eyes logo. The official Cats t-shirt became the second-best-selling t-shirt in the world in the 1980s, second only to the Hard Rock Cafe t-shirt. Merchandising has since become an important source of income for the industry.[313][323]
Within the first 2 days after birth, kittens acquire passive immunity from their mother’s milk.[30] Milk within the first few days of parturition is called colostrum, and contains high concentrations of immunoglobulins.[30] These include immunoglobulin A and immunoglobulin G which cross the intestinal barrier of the neonate.[29] The immunoglobulins and growth factors found in the colostrum begin to establish and strengthen the weak immune system of the offspring.[31] Kittens are able to chew solid food around 5–6 weeks after birth, and it is recommended that 30% of their diet should consist of solid food at this time.[32] The kitten remains on the mother’s milk until around eight weeks of age when weaning is complete and a diet of solid food is the primary food source.[23]
The original Viennese cast included Ute Lemper who played Bombalurina, Steve Barton who played Munkustrap, and Robert Montano who played Pouncival.[112] Pia Douwes was also a member of the cast from 1987 to 1989, covering several different characters including Grizabella.[175] The Vienna production also performed limited runs at the Komische Oper Berlin in East Germany in 1987,[176] and at the Moscow Operetta Theatre in the Soviet Union in 1988.[177]

In the original London production, Mungojerrie and Rumpleteazer were characters in their own right and sang their eponymous song themselves as a singsong-style duet. When the show transferred to Broadway, the song was instead sung in the third-person, with Mungojerrie and Rumpleteazer as puppets being magically controlled by Mr. Mistoffelees. Their number was also rewritten to be faster and more upbeat, alternating between vaudeville-style verses and a "manic patter" section. Eventually, the Broadway version of the song was rewritten to allow Mungojerrie and Rumpleteazer to once again sing their own song as full characters.[388]
By 2012, the royalty payments from Cats to the Eliot estate had totaled an estimated $100 million.[294] Valerie Eliot used a portion of this money to establish the literary charity Old Possum's Practical Trust, and to set up the T. S. Eliot Prize which has since become "the most coveted award in poetry".[337][338] Cats also turned things around for the independent British publishing house Faber and Faber. As the publisher of Old Possum's Book of Practical Cats, royalties of up to £1 million annually[316] kept the then-struggling Faber afloat during the 1980s.[339] Moreover, the musical led to a surge in the sales of Eliot's book.[1] The success of Cats led Faber to turn another of their literary properties, Ted Hughes' The Iron Man, into a 1989 musical of the same name.[340]
November 1985 saw the premiere of a Norwegian-language production at Det Norske Teatret in Oslo. It closed in January 1987 and included performers such as Øivind Blunck, Brit Elisabeth Haagensli and Øystein Wiik.[118][193] Jorma Uotinen directed and choreographed a Finnish production at the Helsinki City Theatre that ran for over two years from September 1986 to December 1988, and featured Monica Aspelund as Grizabella, Heikki Kinnunen as Gus, and Kristiina Elstelä as Jennyanydots/Griddlebone.[194] A Swedish version of the musical opened in 1987 at the Chinateatern in Stockholm. The production was seen by 326,000 audiences before it transferred to the Scandinavium in Gothenburg two years later.[195]

The stage production of Cats has undergone several revisions since its London opening. When the show transferred to Broadway, several cuts and rewrites were made with the intention of appealing more to an American audience.[385] Additionally, a song entitled "Cat Morgan Introduces Himself" was cut during initial development. Lloyd Webber performed this song at the show's 6,138th Broadway performance, when it broke the record to become the longest-running Broadway show.[105]
As of 2017, the domestic cat was the second-most popular pet in the U.S. by number of pets owned, after freshwater fish,[17] with 95 million cats owned.[18][19] As of 2017, it was ranked the third-most popular pet in the UK, after fish and dogs, with around 8 million being owned.[20] The number of cats in the United Kingdom has nearly doubled since 1965, when the cat population was 4.1 million.[21]