I suppose that like most kids, my first exposure to Boris Karloff was the animated The Grinch Who Stole Christmas special. For all the seriousness of that role, it might just as easily be his appearance in Abbott and Costello Meet Boris Karloff, The Killer, in which his character, a Hindu holy man, appears as the de facto leader of a gang of criminals set against the bumbling duo.
By the 1949 film, no fan of Karloff would consider his casting as a Swami to be strange. This sort of role was his bread and butter. Despite Karloff being best known for his portrayal as Frankenstein’s Monster, his career is largely marked with more... exotic roles. In his fifty-two years of acting in Hollywood, the English-born actor played everything from Saracen guards to Native American chiefs. Boris Karloff was a perfect fit for a Hollywood still reluctant to cast minorities. His swarthy face and his penetrating gaze was coupled with a peculiar walk, brought on from years of back problems and bowed legs. Karloff’s intimidating looks made him a perfect fit in a Hollywood that was unwilling to cast minority actors.
Karloff’s first credits silent films were a mixture of Arabian thugs, soldiers, and priests. Even after being cast as The Monster in James Whales’s Frankenstein, Karloff returned to his more usual characters. In 1932 he was Sheik in Business and Pleasure before going on to The Mask of Fu Manchu as the title role. The same year he doubled as Imhotep and Ardeth Bey in The Mummy.
The Mask of Fu Manchu would be the first of seven Asian-themed movies Karloff would make. Karloff’s makeup for the characters of Fu Manchu, James Lee Wong, and the General Wu Yen Fang and the characters themselves are based in racial concepts of the time. For these roles he would don false teeth and tape his eyelids to conform to the public’s expectations of the Chinese. He played both the yellow peril and model minority.  The Mask of Fu Manchu was condemned by the Chinese Embassy in Washington due to its hostile depiction of the Chinese as naturally bloodthirsty towards whites.  Even James Lee Wong, to whom Karloff gave a quiet dignity, is markedly asexual, and though he's a superior investigator, Wong never openly challenges his white counterparts.
Other roles required less in the way of makeup but relied no less on racial expectations. In King of the Wild, Behind that Curtain andAbbott and Costello Meet the Killer, Boris Karloff , he donned hats that corresponded with his character’s ethnicity. In Unconquered, Boris plays Seneca chief Guyasuta and 1940s America’s views of Native Americans are clearly shown in the character’s dress and his defeat at the hands of a “magic” compass.
Though being typecast certainly helped buoy Karloff’s career throughout the 1920s and 1930s, by 1949 even the steady work of foreign villains eventually grew tiresome. His role as Swami Talpur in Abbott and Costello Meet The Killer, Boris Karloff is limited, for the most part, to sitting around glaring at the heroes. With the exception of a 1966 television appearance on The Wild Wild West as a Mr. Singh, Karloff withdrew from the roles in much the same way as he did The Monster.
Karloff, in ailing health, would return to playing the foreign villain in 1971, in what would be his last picture, The Isle of the Snake People .The film itself is forgettable, one of four Karloff made for Mexican producer Luis Vergara. Karloff plays voodoo priest Damballah as well as the villain’s alter-ego Karl van Molder. The Isle of the Snake People borrows heavily from voodoo symbolism and Karloff’s Damballah is no exception, the top hat, cigar and staff are pulled directly from the Baron Samedi character.
While working on Targets, director Peter Bogdanovich asked Boris how he felt about being typecast after the success of Frankenstein. Karloff said he was forever grateful for the Monster giving him a niche,  but Karloff’s niche was already there: the minority villain roles to which he would return to over and over in his long career.
Though many of his villainous roles seem to be marked by negative racial connotations, Karloff never relied on such characterization for his roles. Karloff approached every film as an opportunity to provide his fans with some genuine scares. The fear he could produce in an audience is a product of his imposing presence.
Hollywood’s persistence in casting white actors in minority roles may have helped Karloff’s career, but the partially East Indian actor was not unsympathetic to minorities; Karloff was a founding Board of Directors for the Screen Actors Guild who, as early as the 1930s began advocating for better roles for African-Americans. 
Karloff was an entertainer. He earned his “the Uncanny” billing as a tribute to his abilities to deliver convincingly in the wide range of roles he was given, whether it be a Chinese detective, Indian mystic, Egyptian royalty, or African servant. Intentions for such roles aside, he delivered performances that would never fail to frighten. Karloff’s legacy as one of the enduring faces of horror owes much to these roles. His movies remain popular because of the intensity of his acting and the menace that he could bring to each role.
 The BFI Companion to Horror