Comet

The comet was a rock from space that was heading towards Springfield. Bart discovered it after looking through Principal Skinner's telescope after coming star gazing as a punishment.

History
After the discovery of the comet, they went to the Springfield Observatory and alerted them where they saw it through a bigger, more powerful telescope and found out it was in fact heading towards Springfield. Homer said to Bart that the comet would burn up in the atmosphere and be harmless. After the whole town found out, they headed towards Ned Flanders' nuclear bunker to hide from the comet. However, there was not enough room and Ned was kicked out to suffer from the comet alone. However, racked with guilt, the other townspeople come out and form a ring at the top of a hill and wait for the comet to strike. The comet burns up, hits Ned's nuclear bunker, which falls over from the now tiny rock, and bounces to the top of the hill where Bart catches it and juggles it around for a bit due to it being hot before putting it in his pocket. Bart and Lisa are surprised that Homer was right about the comet.