史密夫 is the Cantonese / Hong Kong rendering of 'Smith', based on Cantonese readings (si2 mat6 fu1, sounding like 'see-mat-fu'). Mainland Mandarin uses
史密斯. Famously, the Hong Kong title for Mr. & Mrs. Smith is
史密夫决战史密妻, a clever pun where
妻 replaces
夫.