The Hangover/Headscratchers

Why didn't he shout for help?
- Assuming it's Doug, no one checks the rooftop (only on occasion), and he was still wasted AND couldn't move due to the sunburn.
- No-one would have heard him. He's high above the street, and the hotel windows are all sealed for the aircon.
Considering where they found Doug, it's almost impossible he didn't die of dehydration. He went out the night before drinking to capacity, then spent the next 36 hours with no water, rain, or shade.
- He did have a sheet....
- It's not impossible to survive, but he was damned lucky.
- The roof wasn't flat. He did have some shade, though only from objects about 2-3 feet high.
Mike Tyson's tiger is only bothered by the protagonists when they're sober.
- That one's an old trick. The animal senses your fear, etc, etc. Whether it's true or not, someone else will have to answer.
- Here's two possibilities. One is that the guys' tension while sober triggered the tiger's aggression, since in the wild a tense animal is either potential prey or a potential attacker. The other is that, while the tiger was comfortable on his home turf as the guys led it into the car, he became increasingly anxious after being away from his territory for a while (felines become strongly attached to familiar surroundings and can take a while getting used to a strange place). It's probably some combination of the two, actually.
Nobody moves in to stop Alan from cutting his palm open?
- Considering the circumstances, they're all standing around, drinking, laughing, and then suddenly someone whips out a knife and cuts himself with it? It's not unreasonable to suppose they'd all be standing there in shock for the second it would take him to complete the act.
Why did Mike Tyson not have a tranquilizer gun? WHO KEEPS A PET TIGER WITHOUT A TRANQ GUN?!?
- If anyone could manage a tiger without a tranq gun, it would be Mike Tyson.
Would you really build a hotel with a roof door that locks automatically, and no other way to get down? What if someone's on the roof when there's a fire?
- Patrons of the hotel are not supposed to be on the roof. It's probably presumed that people who are on the roof for legitimate reasons will have/be given a key to keep it unlocked.
  - Actually The real headscrather is why is the door locked from the outside? Roof door locks are reveresed. The inside is locked while the outside is unlocked. In case someone drops/doesn't have the keys so they won't be trapped. Then again they might have jammed the lock.
Why was Doug hanging out with his friends, looking at pictures, for a big part of his wedding night? Shouldn't he be, you know, with his wife? Or at least mingling with the other guests?
- Guess he had some free time after everything else was done?
- At the vast majority of weddings, it's about the bride. No-one is going to begrudge the groom from wandering off with his best friends for a half-hour, especially towards the end of the night.