This is Russian computer animation from 1968. While the cat itself is drawn, its movements were generated by computer data. It sure looks like a classic cartoon cat, but its leg motion is impressively uncanny. Boing Boing gives us a short translated explanation.
More than 40 years ago in 1968 … A team led by Nikolai Nikolaevich Konstantinov creates a mathematical model of the motion of the animal (cat). The BESM-4 machine, executing a written program for solving ordinary (in the mathematical sense of the word) differential equations, draws a cartoon “Kitty” containing even by modern standards an amazing animation of cat movements created by a computer.
There’s more here, in Russian.