Y'see, the "vegetarian" Marathon burger had (until this week) been made with Burger Up's house-made ketchup, which contains Worcestershire sauce. Worcestershire sauce contains anchovy paste. So the burger was neither vegetarian nor vegan. Nor was the ketchup.
In the thread, another local chef indicated some confusion about what's vegetarian as well, suggesting that diners hand a list of verboten ingredients to servers to take to the kitchen before the meal is prepared. I don't think that's necessary since it really is pretty simple.
(And thanks to the management and kitchen at Burger Up for addressing our concerns so quickly and efficiently. Their Twitter timeline indicates they've already purchased vegan Worcestershire sauce! And clarifying the ingredients of the burger and the ketchup is a service not just to veg*ns, but to gluten-free and kosher customers and those with seafood allergies as well.)
So, for the record, here are some good definitions of vegetarian and vegan (with regard to diet):
A vegetarian eats no animal products or by-products derived from the flesh/bone of an animal. So, aside from meat, vegetarians do not eat animal-derived fat, gelatin, broth or flavorings. This includes lard and and ham-hocks, two common ingredients in Southern cooking. A general vegetarian diet does not exclude dairy, eggs or honey.
A vegan doesn't eat any animal-derived products. All ingredients are plant-based. Many vegans also do not consume products processed with animal-derived products, such as sugar processed through bone charcoal, and beers and wines processed with a substance called isinglass, which comes from from fish. (Not to be confused with isinglass the mineral, a form of mica.)
A lot of confusion comes up with people who refer to themselves as vegetarian, but who actually just don't eat red meat and/or pork. That makes things easier for them, but it's kind of a pain in the ass for the rest of us. That's great if you don't eat some animals, but you're not a vegetarian. You're an omnivore.
That said, here is a list of a items that are (to some) surprisingly not vegetarian:
1. Foods that contain gelatin. Most Western gelatin is derived from rendered animals (as opposed to many Asian countries that use seaweed-based gelatin, also known as agar agar). Gelatin creeps into the craziest places. It's in marshmallows, Altoids, Starbursts (and other candies), Moon Pies, many gummy fruit snacks, a number of yogurt brands, and even Planter's Dry Roasted Peanuts! Thankfully, Goo Goo Cluster revised their marshmallow creme recipe a while back and no longer uses gelatin. And I use Marshmallow Fluff in my Krispie Treats to make them vegetarian.
2. Barbecue flavored chips. Many brands of chips include animal-derived flavorings, including the KC Masterpiece Lay's.
3. Rice mixes. Many prepared packaged rice blends, such as Mexican rice, include chicken stock. Many Tex-Mex restaurants use these same packaged rice blends in their restaurants, too (and have lard in the refried beans).
4. Worcestershire sauce. It contains anchovy paste and is a key ingredient in traditional Caesar salad dressing. Party-going veg*ns avoid Chex Mix, Bloody Marys, and Micheladas because of the Worcestershire sauce.
5. Soup. Any soup is suspect as most use chicken, beef or fish broth as a base.
6. Asian foods. A lot of sauces and soups are made with fish broth or oil. Miso soups, for example, often contain fish flakes or sauce.
7. Italian foods. Even marinara often contains chicken stock and sometimes so does risotto.
8. Vitamins, supplements, and medications. "Gelcaps" are made with gelatin. Don't even ask me how much I spent on non-gelatin capsules when I was pregnant. Or how much vegetarian glucosamine costs. Cha-ching.
Anyhoo, I could go on, but The Vegetarian Resource Group already has a very comprehensive guide on their site. If you work in food service, this is a really handy tool to serve your veg*n customers.