Si and Am

Si and Am are Aunt Sarah's twin Siamese cats are the secondary antagonists later teitary antagonists in Disney's 1955 film Lady and the Tramp and its 2001 sequel.

Both were originally voiced by Peggy Lee. They were later voiced by both Mary Kay Bergman and Tress MacNeille in the sequel; MacNeille now voices them both since Bergman's death.

Development
Earlier versions of the storyline, drafted in 1943 during the war, had the two cats appear as a sinister pair, suggesting the yellow peril. Originally named Nip and Tuck, they came to the house with Aunt Sarah while Jim Dear and Darling were still at home and made Lady look bad by committing a series of crimes such as stealing the baby's milk and robbing the icebox, then pinning them on her. In the novelization of the film by Ward Greene, written during its production, they tearfully expressed remorse over causing Tramp's impending execution by hiding the rat's body as a joke, and then tried to make amends.

Personality
Si and Am are sinister pair of cats who use the love they gain from Aunt Sarah to get others into a large amount of trouble. The cats are sneaky and love to cause trouble and make messes for their own amusement. It is indicated that they care for nothing but each other and take advantage of Aunt Sarah, seeing her as a protector and not as the beloved owner she is.

Physical Appearance
Si and Am are identical seal-point Siamese cats. They are sleek and elegant cream-colored felines with angular, wedge-shaped faces and large, blue almond eyes, which are oval-shaped and narrow out to points near the ends. They have a deep brown facial point with a darker, almost black muzzle, and dark triangular ears. Their noses are black and small, and they both have two middle incisors that hang over their lower lip; these buck teeth are a commonly used Asian stereotype during the late 40s and 50s. Si and Am also have dark brown "stockings" on their front legs and shorter "socks" on their hind legs, and have dark, long, winding tails.

Lady and the Tramp
In the film, Si and Am's owner Aunt Sarah is in charge of Lady and the newborn child. The two cats are commonly seen toted in a picnic basket owned by Aunt Sarah, from which they emerge after her brief departure. While Aunt Sarah is upstairs, Si and Am perform their trademark musical number, "The Siamese Cat Song". During their song, they wreak havoc throughout the household, claiming it as their own, and even attempt to eat both the family fish and family bird. During the closure of their song, Lady ferociously chases after them upon hearing of their intentions to sample some of the newborn baby's milk. Collateral damage ensues, and although the cats caused all the trouble, Si and Am feign injury in order to lay all the blame on Lady, who is then muzzled up by Aunt Sarah as a result. Si and Am are not seen for the rest of the film.

Lady and the Tramp II: Scamp's Adventure
Si and Am reappear in the sequel to the film. They are first seen in the opening of the film while Jim Dear and Darling are taking a stroll in town, where they meet up with Aunt Sarah. She claims she will be attending their family picnic, as Si and Am love Independence Day. They then appear in Scamp's fantasy as he wishes to be a brave enough dog to take on threats like Si and Am.

In the middle of the film, they are last seen attending a picnic with their owner. During the picnic, they are seen attempting to steal the turkey until Scamp arrives and scares them into Aunt Sarah's arms. They are not seen for the remainder of the film.

House of Mouse
Si and Am made numerous appearances in the animated series House of Mouse. In "Rent Day", the cats popped out from their picnic basket, cheering for O'Malley and the Alley cats.

They make a notable appearance in Mickey's House of Villains during the villains' hostile takeover of the club. They are seen singing a part in "It's Our House Now!", and later on witnessing Mickey Mouse's climatic battle with Jafar. In the end, they flee with the other villains, after Jafar is sucked back into the lamp and defeated.

Disney Parks
Si and Am appear in an extremely large amount of Disney Villains merchandise as well as having a statue of them in the Disney Villains Store in Disney's Hollywood Studios.

Fantasmic!
Si and Am appear in the floating bubble musical sequence. Despite various Disney Villains appearing in the show, they appear without aiding The Queen in her plan to destroy Mickey Mouse. Their roles of not being involved with The Queen are similar to Captain Hook and Governor Ratcliffe.

Trivia

 * While Aunt Sarah was often considered the primary antagonist of Lady and the Tramp, Si and Am went on to become recurring Disney characters, and major members of the Disney Villains franchise.
 * These two characters have been cited as Asian stereotypes because of their squinty eyes and bucked teeth (or in their cases, fangs). These features have been altered in the sequel and House of Villains.
 * With their names combined, "Siam" is the former name of the Kingdom of Thailand, referencing the cats' heritage.