Gloria Vanderbilt's youngest son has been using his mother as a foil since he appeared on the Tonight Show with her at age three. Anderson Cooper more recently brought his mother onto CNN to passive-aggressively scold him on Mother's Day and to provide the silver fox some sensible, embarrassing advice on the occasion of his 40th birthday. So when Cooper recently declined to invite his mother on a holiday trip to Egypt — "No! I wasn't going to take my mom," he told a befuddled David Letterman — she was ruthless in her revenge. You might not acknowledge that's what's going on, Anderson, but it's plain as day to the rest of us. (We're speaking of the revenge, of course.) Video after the jump