I did that with a cheap practice line and the cat had a ball.

However a word of warning. The cat would, on occasion, pounce on the knot where the line and leader met. He would grab it with those really sharp claws and that part of the line became a frizzled mess. I have no doubt that there were probably nicks in the leader near the indicator. He also attacked any loops I had on the ground whenever they moved.
So don't use your good line and leader for this.