Advertisement Dreaming of a White Christmas? Looks like you're going to get your wish. has signed on to star in a Christmas movie, the network announced on Thursday. In the untitled film, White's character helps ready would-be Santas for the holidays. But a mystery looms: Is she actually Mrs. Claus? The eight-time Emmy winner and all-around pop-culture legend turned 98 (!) in January. Her Hollywood career spans more than eight decades, and she's starred in such series as , , and . In other Lifetime holiday movie news, the network announced that will star in Merry Liddle Christmas Wedding, a...…Advertisement Dreaming of a White Christmas? Looks like you're going to get your wish. has signed on to star in a Christmas movie, the network announced on Thursday. In the untitled film, White's character helps ready would-be Santas for the holidays. But a mystery looms: Is she actually Mrs. Claus? The eight-time Emmy winner and all-around pop-culture legend turned 98 (!) in January. Her Hollywood career spans more than eight decades, and she's starred in such series as , , and . In other Lifetime holiday movie news, the network announced that will star in Merry Liddle Christmas Wedding, a...WW…