Hippopotamus
From Memory Alpha, the free Star Trek reference.
The hippopotamus (Hippopotamus amphibius) is a large mammalian quadraped native to Earth.
When the USS Voyager was stranded in the year 1996, Neelix and Kes researched Earth television of that time period. On one of the many channels they watched, a running hippopotamus was shown. (VOY: "Future's End")
