Long-time fans of the In-N-Out Burger are likely familiar with the “not so secret menu.” According to the Southern California-based fast food chain’s website, these unofficial items include Double Meat, 3×3 or “Triple Triple”, 4×4 or “Quad Quad”: all options for how many patties you can get added to your burger. Additionally, it includes a Grilled Cheese: a vegetarian friendly option of a cheeseburger and toppings but without the burger, Protein Style: a lettuce wrapped burger without the buns, and an Animal Style burger: a cheeseburger with a mustard grilled patty, pickles, grilled onions and extra sauce.

In-N-Out owner Lynsi Snyder says the popular term “animal style” is named after rowdy customers. In her new book, “The Ins-N-Outs of In-N-Out Burger: The Inside Story of California’s First Drive-Through and How it Became a Beloved Cultural Icon,” she talks about how one night in 1961, a customer spotted Theo Roberts, a then third manager at Store Number 1, prepping a burger with a mustard fried patty, pickles, grilled onions and extra spread.

The customer asked Roberts if he could make him one. After wolfing it down the customer said it was the best burger he ever had. He continued ordering it but didn’t know what to call it, so Roberts told him to order it “animal style.” Snyder says it’s the first known instance of an In-N-Out Burger secret menu item.

While the burger chain has since acknowledged a six of these unofficial items on their website, many who frequent In-N-Out know there’s more to the secret menu. Snyder includes a more expansive breakdown in her book of the different hacks customers have popularized over the years.

In addition to getting your burger animal style, a fan favorite is to get Animal Style Fries: fries topped with melted cheese, grilled onions and their famous secret sauce. The secret sauce recipe has remained unchanged since 1948 and is similar to a Thousand Island dressing.

As far as the burger chain knows, Animal Style Fries were first requested in West Covina in 2002. Customers can also order cheese fries or request for their fries light or if they want them extra crispy they can ask for them to be well done.

When it comes to beverage hacks, a favorite is the Neopolitan Milkshake, a combination of chocolate, vanilla and strawberry milkshakes. If a customer wants to nixs the strawberry, they can order a Black-and-White, which is a chocolate and vanilla shake. Additionally, customers can order a rootbeer float, or any float for that matter, which will combine a soda and vanilla ice cream in a cup.

For those wanting to add a little more flavor to their burger, they can ask for it to be mustard-grilled. Customers can also request pickles or chopped chilies for their burgers. In-N-Out provides their yellow chili peppers whole as well, which provides an extra kick to their menu.

The Flying Dutchman, two slices of cheese and two patties melted between each other, is a secret menu item with a special history to In-N-Out Burger. According to Snyder, the item is named after her father Guy Snyder. Guy’s signature order was two cooked cheese patties so associates began referring to it by his racing nickname “the Flying Dutchman,” a nod to his Dutch heritage.

Customers can also request the Flying Dutchman to be Animal Style where they’ll add a scoop of diced onions to the cheese. Some customers will put a Flying Dutchman on top of their fries and refer to it as “Roadkill Fries.”

Another popular adjustment is the variety of ways customers get their onions cooked. Many know they can get them grilled, but customers can also ask for a whole onion, a circular slice of onion, or a whole grilled onion, that slice of onion but grilled.

Non-food items new customers might not know about is that you can request one of the iconic paper hats that employees are known to wear. Additionally, people can ask for stickers, which provides a fun activity for kids in lieu of a Happy Meal toy.

With a secret menu almost as famous as the fast-food chain itself, we asked a handful of the 23,000 people who attended In-N-Out’s 75th Anniversary Festival to share what their favorite non-official menu items are.

Alan, Gunner and Melissa Mangan from Lakewood, California attend In-N-Out Burger’s 75th Anniversary Festival on Sun., Oct. 22, 2023 in Pomona, California. (Carolyn Burt, SCNG)

Alan Mangan: Flying Dutchman

Gunner Mangan: Animal Style

Melissa Mangan: Grilled Cheese

Christos Sellis (right) poses with an In-N-Out Burger sign at the burger chain’s 75th Anniversary Festival in Pomona, Calif. on Sun., Oct. 22, 2023. (Carolyn Burt, SCNG)

Christos Sellis: Double-Single, Animal Style

Patrick and Emily Tyska, Ari Berkowitz and Will Lentz at In-N-Out Burger’s 75th Anniversary Festival on Sun., Oct. 22, 2023 in Pomona, California. (Carolyn Burt, SCNG)

Patrick Tyska: Animal Style Fries

Emily Tyska: Grilled Cheese

Ari Berkowitz: Neopolitan Milkshake

Will Lentz: Fries Well Done

Ryan Echegaray: Flying Dutchman

Becky Howard: Animal Style Fries

Hailie Encisco: Mustard-Grilled

Tyler Herdenez: Animal Style Fries