There's a young hippo and a 130+ year old tortoise in a Kenyan wildlife preserve who are best friends and they even sleep and play together.
40
Sergeant Stubby was the only war dog to be promoted to sergeant through combat in WWI. He saved his regiment from surprise mustard gas attacks, found and comforted the wounded, and even once caught a German spy by the seat of his pants, holding him there until American Soldiers found him.
16
A koi fish, named "Hanako", was owned by several individuals over many years and lived to be 226 years old, dying in 1977.
6
Dire wolves actually existed, living up to 10,000 years ago before going extinct.
10