In the good old days, Wan Tan Mee was better known as 'Tok Tok Mee'. My mom told me during her teenage years, the Wan Tan Mee sellers used to knock on their stall when they pushed their carts along the back alley. ( actually ' tok tok ' sound is created by knocking 2 bamboo together ) - thanks Mr. Huat and Wong for the information. The sound created was 'Tok Tok'.