Comet's Excellent Adventure - S8-E1
Continuity mistake: When Comet runs after the car, he has his leash on. Then in the next scene, he is still chasing that same car, but he doesn't have his leash on anymore, only his collar. Those things do not just fall off.
Chosen answer: The first time was in the first season, episode 19 "The Seven-Month Itch", the second was in the fourth season, episode 1 "Greek Week", the third time was in the fifth season, episode 19 "The Devil Made Me Do It" and finally in the very last episode of the series, "Michelle Rides Again", season 8 episode 23.
jennibee