Except for those living in the Savage Land, saber-tooth tigers became extinct during the Pleistocene period, the time during which the Earth experienced its last so-called Ice Ages. Saber-tooth tigers were named after their resemblance to modern day tigers (although the saber-tooths of the Savage Land, at least, were not striped), and the unusually long pair of saber-like teeth that each saber-tooth tiger possesses. Saber-tooth tigers could also open their mouths far wider than other members of the cat family can. The saber-tooths' great physical strength and agility and their long, sharp teeth made them the most formidable carnivores of their time, capable of killing animals as large as mastodons and giant ground sloths.
Zabu bore a great resemblance to the best known of the extinct saber-tooth tigers, those of the genus Smilodon, to which Zabu himself may have belonged. Zabu, however, seemed more massive and powerfully built than the known examples of Smilodon whose fossilized remains have been found in North America. Like these examples of Smilodon, Zabu had a very short tail, although some accounts have erroneously portrayed him as having a tail as long as that of a modern tiger.
Saber-tooth tigers, as well as many other forms of prehistoric life, even including dinosaurs, survived into recent times within the Savage Land, a hidden jungle in Antarctica whose tropical climate was maintained by the heat of Antarctic volcanoes. It was in the Savage Land that Zabu was born. While Zabu was still a cub, his mother and siblings were killed by human natives of the Savage Land. Subsequently Zabu was adopted by a family of wolves, but he fled from them after he killed the eldest wolf cub in a struggle for supremacy.
Afterwards Zabu wandered the Savage Land on his own, teaching himself how to survive as he grew to adulthood. A year after his birth Zabu first encountered the female who became his mate.
Maa-Gor, leader of a tribe of primitive Cavemen living in the Savage Land, had been leading his people in exterminating saber-tooth tigers, nearly rendering them extinct in the Savage Land. Maa-Gor and his men killed Zabu's mate. Enraged, Zabu tracked them down and found them about to attack the young boy Kevin Plunder, who had come to the Savage Land with his explorer father, Lord Robert Plunder. Maa-Gor and his men had just killed Kevin's father, and probably Maa-Gor would have then killed Kevin had not Zabu suddenly leapt on Maa-Gor from behind. Zabu scattered the tribesmen except for Maa-Gor, who, unseen by Zabu, was about to kill the tiger with his spear. But before Maa-Gor could do so, Kevin Plunder shot Maa-Gor in the shoulder with his father's gun.
Zabu realized that Kevin had saved his life, and the two became companions. They went to dwell in the Place of Mists, a region where Maa-Gor's tribe refused to set foot. There, Kevin grew to manhood, protected from all dangers by Zabu. It is said that Zabu did not age during the years he was exposed to the strange gases within the Place of Mists. Maa-Gor's people referred to Kevin as "Ka-Zar," which meant "son of the tiger."
Zabu remained Ka-Zar's companion when Ka-Zar became an adult. After Ka-Zar again made contact with people from outside the Savage Land, he often brought Zabu with him on his journeys to the outside world. Zabu also accompanied him to the home dimension of the Sheenarians.
Along with Ka-Zar and his wife Shanna O'Hara Plunder, Zabu escaped the destruction of the Savage Land at the hands of the alien Terminus. Zabu remains the loyal companion of Ka-Zar and Shanna, but the current whereabouts of these three are unknown.
Zabu was unusually intelligent, and, although he was a savage opponent in battle, he was loyal and affectionate to Ka-Zar and Shanna, and could even be playful with them
When Reed Richards is looking for the Infinity Gems so that they do not fall into the wrong hands. Instead they fall into the mouth of Lockjaw, who decides that he will form his own team of heroes to find the lost gems. Joining him are Throg, Lockheed, Redwing, Hairball, and Ms. Lion. Looking for a second gem leads them to the Savage Land, and a T-Rex. They find themselves in the Savage Land face-to-face with a T-Rex. Zabu arrives and helps them run off the dinosaur and is invited to join the team. They sense the location of the next gem in the past so they transport into the prehistoric past and run into Devil Dinosaur, who happens to be protecting its nest, which inconveniently is the location of the gem. They manage to distract Devil Dinosaur while Lockjaw and Ms. Lion get the gem. They then transport themselves back to the present, only they appear over the open ocean. They crash into the ocean, but are saved by Namor's Honor Guard turtles, who agree to help them find two more of the gems. Unfortunately, they are inside Giganto. The turtles flee and Hairball finally freaks out about so much water, waking up Giganto, who swallows them. Inside, Ms. Lion finds the gems, and they teleport away to the location of the final gem, the White House. The final gem is located in the Bo's collar. Bo takes off barking out the front door, and the Pet Avengers follow, only to run headlong into Thanos. He was the previous owner of the Gems when united as the Infinity Gauntlet, intervenes and kills Ms. Lion. The other animals are angered by this act and use the Gems to strand Thanos in an alternate dimension and subsequently revive their comrade. Retrieving the final Gem, the group decides to separate, but not before Throg advises that they now share a psychic link and will reunite if needed. Ms. Lion resurrected by Hairball via the Soul Gem dubs the group the Pet Avengers. Lockjaw presents the Gems to a surprised Reed Richards.
Avengers vs. Pet Avengers
The Pet Avengers stop the robbery of a candy store, have some character moments in the park, then telepathically recognizing the distress of The The Avengers, teleport themselves to Thor, Captain America, and Iron Man only to find they have been turned to frogs. The villain is none other than Fin Fang Foom followed by a legion of Dragons who then proceed to swallow whole everyone but Lockheed.