Mc 10:35 is different, iirc it’s an egg McMuffin mixed with a McDouble. McGangBang is McChicken in a McDouble.Some people call it the "Mc 10:35", since 10:30 am is when most McDonald's stop breakfast service.
The only “official” secret menu item is the Daily Double, and it’s just a McDouble with lettuce, mayo, and slivered onions. It’s just an old menu item that carries on. You’re just making a custom order. Best chance to get away with ordering a McGangBang by calling it that is at like 1 am. Overnight crews do not give a fuck. Some crews would even make you quesadillas if you asked.