I've never seen mayonnaise ON french fries, but in Belgian restaurants I see that pommes frites come with a container of mayo (aoli) on the side and you DIP one fry at a time into it. Just a little. It's not SPREAD over a pile of fries like ketchup. Maybe some places spread it over but I haven't seen that.
I''m kinda surprised gumbo hasn't been mentioned. Wikipedia will usually says it's a soup or stew. I disagree. It's its own thing. I fix chicken soup, chicken stew, and chicken gumbo and they are all very different from one another. Well, chicken stew is closer to chicken gumbo than chicken soup is. But we call it chicken fricassee.
Cajuns may state forcefully that gumbo has NO tomatoes in it. That's New Orleans style. I disagree with that too. I grew up in Vermilion parish which is one of the most Cajun parishes there is., Even when I went to school the cafeteria ladies fixed okra and shrimp gumbo and it DID have a little bit, not a lot, of tomato in it. It was definitely NOT a New Orleans recipe. I doubt those cafeteria ladies knew any New Orleans recipes! My mother used a little and so do I when I make it.
How do you dress your hamburgers? I put ketchup on the bottom bun and mayo on the top bun. Lettuce and tomato and top of the patty.
For steamed or boiled shrimp or crawfish a lot of Cajuns fix their own sauce at the table -- a mixture of ketchup, mayo, and worcestershire sauce. For oysters you vary that with a little bit of horseradish. Restaurants used to put all those ingredients on the table and you fixed your own sauce at the table.
I don't know why but in English we don't say make something, we say fix something. But in French we DO say fait (make or do). Even in A Confederacy of Dunces, set in New Orleans, the characters say "Fix me a weenie" (Make me a hot dog) to the Lucky Dog representative. I guess it's both Cajun English and Yat.