There's a wonderful guy on FB and insta (and probably twitter but I don't know) who does them all and writes about them. His pages are open, so if you find Michael Gabriel, you can see his experiences.
He is a serious runner who doesn't just prep for races, and he runs all the disney races (and most of the others he does) in serious costume. As in, he ran the 2020 half or full in a SUIT, dressed as Walt, carrying a Mickey plush. In the rain. And it was a real suit, not running gear made to look like a suit. And he often dresses as a princess; he accidentally (for real) won the Princess 5K wearing a full dress a few years back.
He then disneybounds based on his costume from that morning and goes to the parks. And he smiles ALL the time.