The Hitchhiker's Guide to the Galaxy (2005) - 4 questions

Question: How did Marvin get the point of view gun to function the way it did (The front part popping open and firing a huge, wide-coverage blast)? That never occurred any other time the weapon was fired, and Marvin couldn't have known how to do it since they had recently discovered the gun.

Answer: Marvin does have a brain the size of a planet! He could have easily worked out the controls or directly interfaced with the weapon.

Question: Anyone who's read 'Life, The Universe & Everything' will now why the bowl of petunias thought 'Oh no, not again' just before it plummeted towards Magrathea, but had Douglas Adams already conceived that backstory and just couldn't fit it in to the narrative at the time or was it something he only came up with when writing part 3?

Answer: Because it was a radio show originally, Douglas Adams would write broadcasts from show to show. He did not know where something would lead, which let the plot become random and funny. So ultimately it was originally created to be funny, then he found a way to link it back in later.

Question: Does anybody know why Zaphod has two faces and not two heads? In the book there are two separate heads and he never gets one cut off. Was this a deliberate choice by the filmmakers for a reason? Thanks.

Answer: It was a choice by Douglas Adams prior to his demise, largely to avoid the large amount of effects required to continuously portray a character with two heads. It was also probably prompted, at least in part, by his dissatisfaction with the second head used in the 1980's TV version, causing him to think of other ways that Zaphod could be portrayed.

Question: What was the purpose of Arthur borrowing Marvin's arm?

Answer: He's trying (very badly) to pretend that it's a weapon of some sort.