Flan is the mega evolution of Pudding created in Evil Land to do something, we do not know, but history is not important. It is similar to Gelatin in ways like texture, but unlike Gelatin, Flan is deadly.
The most famous person who likes Flan is the aptly named, "King of Flan." He made his own brand of Flan that was banned because why not? He also created the word, "Flantasy" which means, "well prepared" but it was outlawed too. Flan is very popular in Japan for no reason, this lead to many thinking it's from Japan. Consumption will lead to Cooties, Peter Pan syndrome and death.