When you open a fresh jar of peanut butter do you only work through one side until it is completely empty then start on the other side?
Or when you get those shallow tubs of hummus does it have to make it back home undisturbed? Then one of the baggers at the grocery store shoves it sideways into the bag completely ruining the symmetry.
If I can't eat a combination of the main dish and a side, the side doesn't go with the main dish. Lucky for me, that is generally the case with most foods.
Desserts are the exception, but I don't count them as sides.
All I can think of off the top of my head would be different food styles in a buffet. Like sweet and sour chicken + sauerkraut or something along those lines. I love them both in their own context, but wouldn't put them on the same plate at the same time.
Their chocolate milk taught me how to burp on command. I remember sitting at the table and taking a big drink which suddenly gave me insight to how it would work, so I did and tossed the biggest belch I’d ever made out there on the table. My eyes went wide and I looked up at my parents and just yelled ‘I figured it out!’ Their faces of disgust slowly changed to faces of confusion while I was just laughing and cheering and belching.