Cujo

Cujo was the first wolf Nova tamed in his Minecraft series.

"Birth"
Cujo was first found wandering around one of Nova's test worlds made for his video about the Minecraft Beta 1.4 update. He wanted to show off the wolves that were added and after searching through his world for what seemed like forever, he finally found a wolf on a random snowy mountain. He quickly tamed it and named it Cujo.

The Death of Cujo
While Nova was building a house for Cujo and himself, night started to befall his world and he wanted to test

Cujo's fighting skills against monsters and after taking out a creeper, skeleton, spider, and zombie, Nova attacked

another Zombie and told Cujo to finish him off, and when Cujo tried to attack him, Nova accidentally hit him and killed him.

In the next episode of Nova's survival world he claimed that Cujo faked his death as an April Fools joke and made him dance.

Tri-Mountain Survival
On Nova's Tri-Mountain map, he tamed one wolf, which he also named Cujo, and several mini-Cujos. At some point, big Cujo disappeared but due to the discovery of Stank Ass 2, Nova held out that he could have still been alive. The mini-Cujos also tragically died as a result of several freak mob and turrets accidents.

Tree Fortress
In episode 65 of the Tree Fortress 3.0 series, Nova tamed another wolf near the first treehouse and named it Cujo. While Nova was powering up a rail system, Cujo followed him up and subsequently fell off, falling to his death. Nova didn't even realize his wolf was dead until after finishing powering the rails.

Trivia

 * Cujo was both tamed and killed in the same recording, though in his next recording Nova insisted that it was just an April Fools' joke and had another Cujo.
 * Most of Nova's wolves are called Cujo, apart from the wolves tamed in Hershel's Land.
 * Cujo's name most likely comes from the Stephen King horror book "Cujo", in which a St. Bernard named Cujo is bitten by a bat causing him to contract rabies and start killing people.