A Liger is a Lion/Tiger.
Biography
Ligers are real animals. You can spot them when you see a lion/tiger type cat, with a mane, and stripes. In the series, Napoleon states they are bred for their skills and magic. It is pretty much his favorite animal. In the animated series he meets liger Shasta.
Trivia
A real-life liger does look like what is shown in Napoleon Dynamite.
Gallery
Napoleon's drawing of a Liger
Shasta the Liger
Liger's sleeping at a Liger Farm