Naomi Watts is wishing her son Sasha a happy 16th birthday. The "Mulholland Drive ... "Happy 16th to my darling boy," she wrote in the caption. "I cannot believe how fast this happened?!

“I can’t believe that I’m actually writing this but.... a very happy 16th birthday to my firstborn baby boy @kingsrossdale_,” the “Hollaback Girl” singer wrote alongside a throwback pic.