"Taiyaki," a fish-shaped pancake of sorts made of flour and filled with "azuki" sweet bean paste, has been around for a century.
It's as commonplace as "daifuku" sticky rice cakes with the same bean paste and "watagashi" cotton candy.
Taiyaki became all the rage when "Oyoge! Taiyaki-kun" ("Swim! Taiyaki") emerged as an extremely popular children's song in 1976. Since then, innovators have offered variations in filling ranging from custard cream to sesame seed cream to cheese and sausage — anything to put between the batter and keep customers engaged.