Pitch Black (film)/Headscratchers

The planet that eclipses the sun is a massive ringed planet. Even though the planet is big enough to block the sun by itself, some dim light would have been diffused by the rings and reflected to the planet. Then the fact that until later in the movie when it rains we have absolutely no reason to believe it is cloudy - the sky is clear up to the sun being eclipsed. That means stars should be out, and lots of them. Anyone who has been out away from a large city can attest to how bright a sky full of stars is. SO... plenty dark? Yes. Pitch black as they show it to be? Doubtful.
- Maybe the system is in a nebula or otherwise has the stars obscured.
- Or the starlight is just exceptionally dim in that region. Maybe the atmosphere has some quirk that causes any non-planetary light source that's not particularly large (like the sun) to be blotted out.
The planet that eclipses the sun pops up from under the horizon in quite a hurry, quickly blocking the sun. THEN, completely violating inertia, stops dead in front of the sun for god-knows-how-long. There would have to be massive forces at play on that planet to stop it like that - forces which would rip that planet apart.
- The other planets in our solar system stop and reverse themselves - as seen from Earth. It's all about how the orbital timing is. Their motion is around a common center point, not around each other. Also, it's a gas giant, and obviously fairly close: Even if it keeps moving at the speed we see, it could take most or all of a day for it to move out alignment with the sun it's blocking.

They've left a spaceship to bake on a hot, desert planet. Then they seek refuge inside of it. It should be like an oven in there, without power to operate the ventilation system.
- It's not like they had a better option.
- It obviously is hot in there, but there's probably a fair bit of insulation of some sort too that keeps the heat from becoming deadly.

When the ship crashes in the beginning, the front windshield is shattered. Debris pummels the pilot, who gets up after the crash without a scratch - even though at the speeds the debris would have been coming through the windshield a grain of sand would become an unpleasant projectile.
- Maybe there was some sort of inertial dampening field between the screen and the pilot for just such a situation. Tech levels vary a lot in this setting, it's not that implausible.

The creatures appear to have wiped out all other life on the planet except for the glowworms. How do they survive with no food sources?
- We don't know that. The characters only explored a tiny fraction of the planet; Life on the surface is strongly implied to be destroyed, but there could still be a very complex ecosystem underground, perhaps drawing energy from volcanic activity, which happens deep in our oceans where sunlight doesn't reach.
- There are smaller, winged creatures. Possibly those reproduce very quickly and are also a food source. (Assuming they're not just a juvenile stage of the big ones.)
Why would subterranean creatures who can only come outside once every twenty years or so evolve flight?
- Massive underground caverns?
- What he said, plus during the eclipse (which is said to be "lasting", so it's not like they only get a day outside), they'd probably be ranging quite a bit to hunt and mate, so wings would still be something valuable. Besides, we don't know how long they live... if they live to be 200, that's still 10 eclipses each of them would go through, they'd see plenty of use of their wings over their lifetime, no reason for them to lose them in evolution.

Wouldn't they be able to build a solar-powered vehicle that can STORE A CHARGE in the future? What's the use of having a vehicle that can only operate when it gets hit by direct sunlight?
- The vehicle seems to have been designed for this planet, where it usually doesn't get dark. Not having a battery onboard saves weight and expense.
  - Honestly I think this was the question. The "colony", which seems to have just been a few buildings and was thus more like an outpost or survey setup, seems to have not known about the extended eclipse and the creatures. They thought it was always bright out, so they brought equipment designed to work on constant sunlight rather than adding the extra expense and weight of batteries.
- You could potentially handwave it as a missing or damaged battery as well. If someone had pointed out "Crap, the battery doesn't work, but at least the suns are out" then it'd be justified. Maybe they just missed the part about pointing it out?

Other than for dramatic effect,why did they ALL go back to the crashed ship and then all return to the escape pod TOGETHER? Wouldn't it been smarter and easier to leave one group at the camp w/ the escape pod prepping it (or just waiting) and have a smaller group bring the power cells back to the camp?
- Sure, but there was no clear leader of the group at that time telling them what it would have been smarter to do.
- Also, no one particularly trusted each other to be left alone with vital stuff. Also, no one really wanted to be left alone. Also, no one really wanted to be left alone with people they didn't trust.

And how were these solar windmills supposed to work? Of course, there are these small versions you can buy at almost any crafts store, but even they need to be built with very very light metal parts that are carefully balanced to even maintain their own rotation when hit by sunlight. I can't imagine them being able to power any kind of machine, especially not an industrial-level generator.
- They look like the solar windmills we can buy anywhere today - that's not necessarily what they are.
- And they may not even power the machine at all; I took them as some kind of analogue gauge to give you an idea of how much sunlight you're getting.

How does a creature that light burns evolve on a planet with continuous daytime?
- How does a creature with no eyes evolve on a planet where we get a full range of the visual spectrum? How does a creature evolve to live in volcanic heat when there's so much cold ocean? How does a creature evolve gills when there's so much air to fly around in? Because evolution is situational and not immediately obvious to any particular random observer.