The Siamese cats are the antagonist in "Growltiger's Last Stand", in which Gus reminisces about a performance in which he played Growltiger, a ferocious pirate who was taken down by the Siamese crew, led by Gilbert / Genghis.
The Siamese cats are portrayed as ruthless, efficient, yet possibly merciful towards Griddlebone. It is sometimes implied that Griddlebone may have been in cahoots with them all along, intentionally distracting Growltiger so that the Siamese can take him down.
The lead Siamese is named Gilbert or Genghis, depending on the production. He usually has a featured moment in which he duels and ultimately defeats Growltiger, displaying his sword-fighting prowess.
As the Siamese are performed by most of the ensemble, one of the male ensemble members will double as Gilbert / Genghis.
In the original London Production, the role was named "Gilbert" (as it is in the original T S Eliot poem) and was played by the actor playing Coricopat. This double track would follow suit in most productions, particularly those based in Europe.
In the original Broadway Production, the lead Siamese was renamed "Genghis" and this name was subsequently adopted by most productions, with alternate spellings including "Ghengis" and "Gengis". Carbucketty initially doubled the role of lead Siamese on Broadway, while Mungojerrie was given the track in the 1st US tour the following year. After the role of Carbucketty was replaced by Mungojerrie on Broadway in 1987, the double track of Genghis was also given to the Mungojerrie actor. Mungojerrie would double the part again in the 1986-2001 Hamburg production, the 5th US tour and the 1991-1993 Zurich production.
In other productions, the following roles have also doubled with the lead Siamese:
- Vienna: Tumblebrutus played Genghis
- Amsterdam 1987/Paris 1989: Pouncival played Genghis
- Japan: An ensemble cat named Gilbert plays the lead Siamese (though in earlier productions Mungojerrie doubled)
- China: An ensemble cat named Grumbuskin played Genghis
See Growltiger's Last Stand for the complete lyrics.
The original London production dressed the Siamese characters in simple, generic "Asian" style robes patterned with triangular blue-eyed Siamese cat faces. The choreography included large fans.
The Broadway production, the following year, had a far larger budget for costumes and the Siamese upgraded to some of the most intricate and complex costumes in the show. Patterned after historic Thai Armour, they included complex headdress, a broad collar with pointed shoulders, and a tabard, worn over fawn to brown ombre satin. The collar and tabard included electrified light-up blue eyes that glowed. They also gained the prop carving knives and toasting forks as mentioned in the lyrics. These more elaborate designs became the standard world-wide and replaced the simple fan costumes in the UK by the mid-1990s.
Despite the reworking of the Crew costumes and score in the London revival, these Siamese designs remained largely unchanged until 2019. At that point they were redesigned for the Vienna revival (as was Macavity). The Asia tour of the following year used these new designs. These costumes strongly reduce the stereotypical 'Oriental' elements such as the exaggerated facial features, yellow 'skin', and ornamented armour and helmets, giving them a more slim and elegant silhouette and changing the palette to black, white, and dark blue.
The portrayal of the Siamese has been condemned by both critics and fans for its dated and offensive racial stereotypes. However "Growltiger's Last Stand" has been gradually phased out in UK and US productions from 2016 onwards.