... I'm gonna get one of those writer planes (or become friends with someone who's a pilot, because apparently renting a plane like that is really expensive) and write "gullible" in the sky.
And it will be the time for those people who always look up when their friends say "Hey look! Gullible's written on the ceiling!" to redeem themselves.
Not that I'm one of those gullible people... well, not usually... but I think it shall be very amusing.
Everyone will be tapping their friend to tell them about the phenomenon in the sky, but their friend won't believe them! Why not? Well, remember the boy who cried wolf? By the time the person's friend actually looks up to see "gullible" in the sky, it will be too late- the word would have dissipated already! And maybe it shall be the cause of many arguments between people....
... and I shall have been the cause!
*cue evil laughter*