British actor Peter Sellers as a Chinese detective. Likely a parody of how Charlie Chan had never been played by a Chinese actor in live action). It is later revealed he was actually either Lionel Twain's illegitimate son or adopted and raised by Twain. In either case, no explanation is given for his speech.
The American actor James Coco plays Milo Perrier, who (depending on which line of dialogue you believe) is either a Frenchman or a Belgian.
Milo Perrier: Never underestimate a Frenchman's nostrils, Miss Twain.