Ketchup has no place on a hotdog. Mustard is the gold standard. Chili, cheese, dijon, and caramelized onions are all acceptable. Tomatoes, pepperoncini, sauerkraut, and pickles are also OK. I have never heard of mayo on a hotdog, is that a Canadian thing or something? I am thinking Canada because they put it on their fries.
Chicago makes the best hotdog. https://en.wikipedia.org/wiki/Chicago-style_hot_dog
Lets get down voted together by being correct!