In 1986, Halley's comet did a drive-by of the inner solar system and the Twice in a Lifetime wonder turned out to be a total flop. [see Comets in Specials 1]. In 1994, comet Shoemaker-Levy 9 put on a spectacular show when it was broken into bits by Jupiter's gravitational field and slammed into the giant planet with the Hubble space telescope watching.
Also in 1994, the weird announcement below appeared in various newspapers. Proving that people can always find the money to waste on a nutty cause.