Wikisimpsons - The Simpsons Wiki
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. Mayor Quimby came to the city for a conference about the comet, where Professor Frink told everyone they were going to launch a rocket to destroy it. The rocket skipped the comet and instead destroyed the only bridge out of town. People then found out Ned Flanders had a bomb shelter, so they headed towards it 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.
The comet is currently in the possession of Bart Simpson, and is willing to show it to anyone who'll pay him five dollars and do a perfect impression of Huckleberry Hound