Actually Skip, I believe there's no such thing as a "Big Mac Happy Meal". A Happy Meal is aimed at children (though enjoyed by diners of all ages) and is typically available with hamburger, cheeseburger or Chicken McNuggets. The Big Mac can be purchased a la carte or as part of a Big Mac Meal.
Iceberg lettuce? I hope this is not being suggested as one of the ten most compelling reasons to eat more like a vegetarian. Now, a little endive salad with pear, walnuts and gorgonzola, that's a different matter entirely.
"The number-one reason for eating a plant-rich diet is that it tastes good. The five vegetables that Americans eat most are French fries, tomatoes (mostly as sauce or ketchup), onions, iceberg lettuce, and other potatoes." - Bonnie Liebman, Ten Reasons To Eat More Like A Vegetarian, godsdirectcontact.org, cited 25 March 2009.