As an employee of In-N-Out Burger I am in on all the things we can offer customers. My manager even quizzed me on everything! Needless to say, I easily passed and recieved a raise from the minimum pay of $8.25 to $8.50 (Please keep in mind that in California the minimum wage is $5.75). Here are some other items:

Burgers
Whole grilled onions: Entire slices of onion which are grilled and put on the burger. One regular customer had 10 of these put on his burger.

Fries
Fries light: This option tells the fry person to pull the fries before they are fully cooked to a golden brown. My sister descirbes them as "mushy fries". Some people enjoy "20 second fries" leaving them virtually uncooked.
Fries with cheese: A melted slice of cheese is put on top of the fries for about $.20 more.

Shakes
Root Beer Float: Half vanilla shake and half root beer. I have never had this ordered before, but I sure know it can happen!

Drinks
Virtually any combination of drinks can be ordered. Common combination include: lemonade/tea, lemonade/7-up, and tea/7up.

Well, I think that about completes the list. If you go to an In-N-Out and order any of these things they should be happy and willing to oblige you. If not, just tell them how it is done. Happy eating! By Request: My opinion of why these items are "hidden" is to encourage regular customers to get to know the inner workings of In-N-Out and be proud that they know something that most people do not know. Don't we all love knowing something that other people don't? The menu hasn't changed since In-N-Out was first opened, so why should it change now? This is my opinion entirely, but I hope you see some sort of validity in it.