Imagawayaki (今川焼き) is a Japanese dessert often found at Japanese festivals as well as outside Japan. It is made of batter in a special pan (similar to a waffle iron but without the honeycomb pattern), and filled with sweet azuki red bean paste, although it is becoming increasingly popular to use a wider variety of fillings such as vanilla custard, fruit custards/preserves, curry, various meats, vegetables, potatoes, or mayonnaise. Imagawayaki are similar to Dorayaki, but the latter are two separate pancakes sandwiched around the filling after cooking, and are often served cold.
Imagawayaki began to be sold near the Kanda Imagawabashi bridge during An'ei years (1772–1781) in the Edo period. The name of Imagawayaki originates from this time.
(From Wikipedia)
The Imagawayaki is famous for its numerous names, regional and store brands, "Imagawayaki" even just being the primary name in the Kantō region. The main joke involving this treat is really just pointing out it has many names, making a new name for it, or identifying a character's native region by how they name it. The only name that reached any sort of consensus is "Baked Mochocho" and it's only because it's a ridiculous joke name.
