Unagi

An Unagi is a species of eel that first appears in the Nintendo 64 game Super Mario 64. They later appear in New Super Mario Bros. as a enemy that appears in underwater levels. Their name comes directly from the Japanese word for eels, unagi. During some underwater levels, Unagis would swim around in a predictable pattern trying to hit Mario or Luigi. Some Unagis also live in small underwater coves, attacking anything in its vicinity. There is also a big version called the Mega Unagi.

Several Unagis reappear in Mario Kart Wii, where they can be seen while traveling through the underwater tunnel in Koopa Cape, poking their heads out of various Pipes. Another, perhaps a Mega Unagi, can be seen swimming outside of Chain Chomp Wheel.

They also reappear again in Mario Kart 7, making a cameo in the underwater zones of Daisy Cruiser and Koopa Cape. In Mario Kart Arcade GP DX, they appear in the underwater parts of the race track Tropical Coast.

A single Unagi (a Mega Unagi) appears in an underwater section of the Mario Kart 8 track Dolphin Shoals, where players race along its body for a short section and be able to perform Tricks.