The preserved corpse of a sabertoothed tiger found in the Megakat City Tar Pitys. It was an exhibit at the Megakat City Museum of History. When the Pastmaster came looking for the Tome of Time and was accosted by a security guard, he used his pocketwatch to bring the tiger to life as a zombie. The creature attacked the guard, who wound up buried under a collapsing dinosaur skeleton, and then chased Deputy Mayor Briggs and Dr. Sinian to the roof. Here, the undead beast encountered the arriving SWAT Kats. Although T-Bone looked eager to grapple with the monster, Razor quickly took care of the beast by shooting it with the Turbokat’s cement machinegun; the sabertooth wound up completely encased in cement and plastered to the wall.
The script for The Pastmaster Always Rings Twice describes the tiger as being much more skeletal than it appears in the final version of the episode, explaining why Dr. Sinian specifically refers to it as “ancient bones.”