I remember my student days where breakfast consisted of cold pizza and warm, flat beer. Chilli & beer, curry & beer. Fried, left over baked potatoes and beer
All perfectly acceptable breakfasts IMO.
I like a nice omelette for breakfast but people think that is weird for some reason. Scrambled eggs seems to be fine. My little sister would only eat egg mayo sandwiches for breakfast for about 4 years. We didn't have mayo in the house so used salad cream but still called them egg mayo.
Toast, that wonderful breakfast food, seems to be acceptable any time, day or night. Now, that's a flexible food.