I'm not sure if this is the right place to pitch a myth idea but rest of the forum areas seemed unsuitable. So here:

Explaining UFO sightings with swamp gas, weather balloons, planet Venus etc. seem questionable to me.
I've seen a runaway weather balloon once and it did look a bit strange in broad daylight, but nowhere near enough to confuse it with an alien space craft.

I would like Mythbustes to test if common UFO explanations have any merit. Can you create a situation where someone mistakes balloon, swamp gas etc. as UFO.

While they are at it, they could also prove that making crop circles with some string and a board is possible.

Additionally there was one MacGyver episode where someone created a UFO illusion with power lines going over fertilized field. Testing that could also be interesting.

The swamp gas explanation was used once by a skeptic and it is always dragged out by the believers. Venus accounts for 3/4 of UFO sighting. Watching the news years ago, I saw a news story about a UFO that was reappearing night after night over the span of a week. Some yahoo bought a cheap telescope and started looking at the sky. He saw a hovering object that would dance around and reported it to the local news station. The man pointed out the object to the cameraman, who filmed it and they showed it on the news. An astronomer identified the object as Arcturus but this guy wouldn't believe it. He said, "I know what I saw and it wasn't a star."
I think people who report UFO's that turn out to be mundane objects are embarassed about looking foolish so they start embellishing their stories.

Crop Circles have been done to death. There have already been many shows that recreated crop circles.