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troperville

The "grand finale" of Springfield Elementary's Science Fair, the launching of a weather balloon, turns into a laughingstock after Bart makes some secret changes that turn it into a floating effigy of Skinner with his pants down and a sign reading "Hi! I'm Big Butt Skinner!". Naturally, it doesn't take long for Skinner to figure out the culprit and thus Bart is forced to aid him in his amateur astronomy...at 4:30 AM. While there, Skinner expresses his dreams to have an object in the sky named after him (he did find something once but was beaten to the punch by "Principal Kohoutek

"). Several boring observations later, Skinner spots...the baloon, which he attempts to take down. Bart then screws around with the telescope and spots a comet in the sky, which he reports to the Springfield Observatory via Skinner's cell phone. Skinner arrives clutching the balloon and takes the phone...just in time to be told that Bart just discovered a comet. Cue Big "NO!"...which causes Skinner to release balloon prompting a second Big "NO!"... and a paper boy throws a paper at his feet with the head line "PREZ SEZ 'SCHOOL IS FOR LOSERS'" prompting a THIRD Big "NO!".

Bart's discovery is noted by the press and Bart is invited to join the "Super Friends", a group of nerds (naturally Bart isn't interested). The mirth is short lived though since the comet is suddenly on a collision course to Springfield. Professor Frink then announces that they will destroy the comet using a missile. The missile is launched... and it misses the comet completely, instead destroying the Only Bridge Out Of Town, cutting off Springfield's only hope of escape.

After Congress fails to help, Homer tries to calm his family by saying the comet will burn up on reentry, which they don't believe. This prompts Homer to take the family to Flanders' bomb shelter. However, it turns out that it's the only shelter in town since everyone else tries to get in. Unfortunately, the door won't close, meaning SOMEONE has to get out. Each person then starts making the case why their personal contributions are necessary to the "future". Eventually Homer suddenly decides that there's something the "future" WON'T need: Left handed stores, i.e. Flanders. Flanders calmly accepts and leaves, only for Homer to start feeling guilty and leave to join him. Eventually the entire town converges on the hill where Flanders to await the comet's arrival...which burns up on reentry just like Homer said. While the rest of the town decide to burn down the observatory so "this will ever happen again", The Simpsons are left creeped out at Homer being right.

This episode has the following tropes:

Achievements in Ignorance: Skinner has been at his astronomy for years, makes very calculated and precise adjustments with his telescope with the hope of finding something interesting, and has ultimately turned up nothing. Bart screws around with the telescope for a few seconds, spins it around haphazardly, and discovers a comet.
Big "NO!": Skinner unleashes four of them over the course of the episode.
Brick Joke: A running one involving the "Big Butt Skinner" balloon.
The Cuckoolander Was Right: Early on, Homer shrugs off the comet's perceived threat, claiming that it will burn up in the atmosphere and end up "no bigger than a Chihuahua's head." That's exactly what happens, complete with a nearby Chihuahua for comparison.
Bart: "And the weirdest thing of all is that dad was right all along."
Homer: "I know kids, I'm scared too!" (The family hugs together, terrified)
Irony: Out of all people in the shelter, the one to leave was Ned Flanders, who built it in the first place. Also, the shelter crumbled to "Big-Butt-Skinner" baloon.