Iguanas are vegan
While some wild specimens have been known to occasionally feast on insects, iguanas are at their healthiest when they consume an all-vegetarian diet.
"No iguana, even a young one, should ever be fed meat, dog or cat food, insects or any other kind of animal protein," according to the Green Iguana Society. (The website is no longer functioning.)
Of course, just because they're vegetarians doesn't mean they can eat just any plant. For example, vets strongly discourage iguana owners from feeding the creatures too much cabbage or kale as it can cause goiter. Lettuce is yet another vegetable that should only be given in small quantities due to its low nutritional value.