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1) Why was there a fat soldier?
To merely provide comic relief. He is the cowardly lion, if you will. He talks big, describing how he named his guns, but in truth is more of a coward. As for why Dalton wanted to keep him in the squad, it was merely for troop morale, to amuse his men. Granted, not a very smart move since it makes him more of a burden than anything, but I suppose it depends on the officer in command.
2) Why were the Special Forces guys so stupid?
The whole idea was to make this a kind of horror-comedy, not to do something along the lines of something like THE TEXAS CHAINSAW MASSACRE. Also, the whole story was about the conflict between the AMS and Special Forces due to the obvious inexperience of the latter. They had never dealt with zombies before.
3) What is AMS?
AMS is the zombie-hunting organization in the game from which this is based on. It is not known what it stands for, although some refer to it as "Agency for Mystical Services" or (most likely) "Allied Mercenary Society".
3) Why did Professor Curien cut the girl's clothes?
As a scientist, he wanted to observe any changes to the phenotype, that is, the physical characteristics, of the subject when injected with his latest serum.
4) Why did the girl try so ridiculously hard to open the van doors?
To get the radio.
5) Why did that soldier wander off after the girl despite the knowledge of her possibly being a zombie?
He didn't know that it could be one. How was he to know that zombies cried (or mimic crying)?
6) When the hell had zombies started to smell?
They were sniffing in the film, it's just that sometimes the music prevents one from hearing them.
7) At one point, Ellis shot a zombie and had wiped the blood into his mouth. WTF?
That was an error that couldn't be corrected due to a short budget and a very busy schedule. Maybe he turns later on after the film.
8) Why wouldn't the soldiers fire their machine guns?
Some of guns were jammed during production, though it could also be due to lack of budget that prevented more in the way of gunplay.
9) Why would Ellis do something stupid as slopping guts onto his own body? Wouldn't he be infected by the blood?
He slopped zombie guts onto himself so that he would smell like the creatures themselves. As for infection, no, because it was made clear in the film that the blood has to be within the body in order to have its effect.
10) Why the hell would a horde of zombies not leave the university for 29 days?
Anyone who has been to university would know that campuses are huge, therefore there should be a sizeable food supply. However, that does not apply to all of the creatures. The film indicates that some had left the confines, such as the reanimated Curien, who attacked the French chef. The whole 29 days thing was an in-joke to the film 28 Days later.
11) Why the hell would zombies develop super-sized teeth to penetrate armor when this is the first encounter?
This was not the first encounter. Caspar had indicated through her briefing that various platoons and Recon were sent in, but had failed to make it out alive. It also depends on both how the infection was altered and how fast it mutates a host.
12) Why couldn't they take more samples?
This was left unanswered by the writer, but it's possible to assume that the pack that zombie had grabbed from Ellis contained more vials.
13) Why was Caspar there?
She's not the same one. Similar character, but different altogether. The Caspar from LOVESHACK OF THE DUD was Coast Guard, the one in this film is a Colonel from the US ARMY.
14) Why wasn't Bart infected?
It was a mosquitto bite. Since he had cut off his own hand, the bloodloss slowed or possibly stopped the infection from taking over.
15) The AMS are supposed to be an international agency yet there are only two agents. What's with that?
That is plain retarded. It's like saying that the SPECIAL FORCES in the film is all that the US ARMY consists of.
16) If they're a secret organization, why did Nightingale tell the guy at the beginning what she does for a living?
The guy lied to her, saying that he was a neurologist, when in fact he was a BLOCKBUSTER employee. In turn, she paid him back in kind. The zombie infection was being covered up, which was why Ellis explained to a girl that there was food poisoning.
17) What's with the ending, with Ellis talking to Nightingale? Are they retarded?
No, he was just raising the possibility of one of their comrades on some other mission finding the cure, or let alone the possibility that the infection could die out, despite knowing the fact that they had f3cked up their mission to retrieve the sample. It's wishful thinking.
18) How had Nightingale escaped?
The film crew wanted to have a scene revealing that the table was moveable, but again, it all came down to time and money.
19) Why couldn't they take the sample, even though it was smashed?
The whole purpose was to get a blood sample, not a DNA sample. DNA could be from anything like hair, skin, etc. In this case, they needed an uncontaminated sample from Patient Zero. Because Bart blew himself up, not only had he destroyed the vial, but the possibility of it being contaminated with his own blood is greater. They could have tried taking the broken vials, certainly, but the possibility of being cut by the glass or having it coagulate onto one's own shirt is something to consider.
20) What's with Private Rodriguez?
Originally, her character was supposed to be a male, but because an appropriate actor couldn't be found for the role, Rodriguez was changed at the last minute.
21) Are there Privates in Special Forces?
Yes, there are.
22) Why is this called House rather than School?
Well, in universities, there are grad houses. In all seriousness, though, it's based around the "House of the Dead" arcade games.
23) Why wasn't the van affected by the blast?
Not even the guys who made film knew. Even though they blasted it with some explosives, it was still sturdy.
24) Why send in only one missile? Why not a squadron of planes?
The whole mission was supposed to be top secret. A single missile could be, at a distance, mistaken for something else by any potential eye witnesses. Certain aircrafts can fire a single missile that would be enough to level whole city block. A single missile on its own is far more subtle than a dozen. How the government would try to cover this up is not known but to the writer.
25) Why couldn't those teens hear the creatures behind them?
The zombies were not making any noise.