John Slattery's Mad Men character, Roger Sterling, always seems to have a Gibson in his hand. However, Slattery doesn't quite share the same tastes as his character, especially since the Gibsons he drinks on set are filled with water.
"Isn't that just a martini with onions in it?" Slattery said. "The 'Gibsons' I usually get are actually water and onions. It's five or six in the morning -- they're not giving us real booze."