Red Koi Fish

The Red Koi Fish (similar to sardines) is what you use to summon the Mighty Dragon in Year of the Dragon. When the player shoots red koi fish out of the slingshot, the Mighty Dragon comes and defeats all the pigs in the area. When the player touches an eye symbol next to the pause sign, all the birds disintegrate and a red koi fish hops on the slingshot.

Trivia
In the Year of the Dragon Animation video, The Red Koi Fish is made of gold, and isn't red.