Cow and Chicken - Season 2 Episode 8 Comet!
Overview: Cow and Chicken's class go on a field trip to the Cometorium, where Chicken is bored stiff. After getting hit by one of Dad's golf balls (he was golfing right next door), Chicken hangs it in front of the telescope; soon, the whole town is in panic of the arrival of ""Dad's Ball Comet"".