Where did C-3PO's fussy and worry-prone personality come from?

Question

Droids develop personality with their experience memory. Purging the memory should clear the personality, too. Unfortunately, this didn't work on C-3PO. It looks like this personality is hardwired to him. In the prequel trilogy, he was fussy and worry-prone. In the original trilogy, he was again fussy and worry-prone despite having memory wipe.

If you look at the first version of C-3PO, you'll find that he had the same personality even that time. This brings the question: From where did kid Anakin get this fussy and worry-prone personality data to burn it as fail-safe default of C-3PO?

Answer 1

To the best of my knowledge, nothing in canon or Legends tells us exactly where a droid's personality comes from. Therefore I will provide an educated guess.

We see in Episode II that C-3PO's head was placed on a battle droid's body and a battle droid's head placed on C-3PO's head. There is clearly a personality conflict between C-3PO and the battle droid: the one with C-3PO's head fires its blaster at the Jedi and exclaims (in the battle droid's voice!) "Die, Jedi, die!", and then C-3PO apologizes in his own voice. Here's a video of the scene on Youtube:

From this scene it is apparent that a droid's personality is not entirely dependent on the verbobrain in its head. This information, combined with the fact that C-3PO was constructed out of protocol droid parts Anakin salvaged on Tatooine, indicates that C-3PO's unusual personality is likely affected by odd interactions between some of his salvaged components. A memory wipe to C-3PO's verbobrain would not totally remove his personality since his personality is evidently controlled somewhat by his other salvaged components.

On the one hand, C-3PO's personality is mostly like that of a protocol droid since he was originally manufactured as a standard protocol droid. Putting a protocol droid in stressful, violent situations (as we often see him in the movies) would reasonably cause that protocol droid's personality to be fussy and certainly worry-prone. This is simply because protocol droids would be designed to operate in non-violent situations (like negotiations) and would be very sensitive to the emotional state of individuals around it. If those individuals are stressed and worried because they are in battle then so would the protocol droid.

On the other hand, C-3PO is no ordinary protocol droid since he was salvaged from components from multiple droids. In that sense he has a unique personality that is mostly like a regular protocol droid's but particularly quirky.

In summary: As a protocol droid, C-3PO's baseline personality would likely already be somewhat fussy and worry-prone in the stressful, violent situations we often see him in. But C-3PO is no ordinary protocol droid in that he is composed of components salvaged from multiple droids, giving him an unusual personality that can't entirely be deleted by a memory wipe.

Answer 2

This is covered in the film's official novelisation. In short, young Anakin stuffed C-3PO with all the AOL floppies he could lay his grubby mitts on:

Anakin had only laughed. What use is a protocol droid to a Jedi? Even one as upgraded as 3PO - Anakin had packed his creation with so many extra circuits and subprograms and heuristic algorithms that the droid was practically human.

“I’m not giving him to you,” he’d told her. “He’s not even really mine to give; when I built him, I was a slave, and everything I did belonged to Watto. Cliegg Lars bought him along with my mother; Owen gave him back to me, but I’m a Jedi. I have renounced possessions. I guess that means he’s free now. What I’m really doing is asking you to look after him for me.” “Look after him?”

“Yes. Maybe even give him a job. He’s a little fussy,” he’d admitted, “and maybe I shouldn’t have given him quite so much self-consciousness-he’s a worrier-but he’s very smart, and he might be a real help to a big-time diplomat … like, say, a Senator from Naboo?”

Padme then had extended her hand and graciously invited C-3PO to join her staff, because on Naboo, high-functioning droids were respected as thinking beings, and 3PO had been so flustered at being treated like a sentient creature that he’d been barely able to speak, beyond muttering something about hoping he might make himself useful, because after all he was “fluent in over six million forms of communication.”

Answer 3

There are a lot of "what if's" considering all of the canons. My best guess is that there is likely a permanent personality program that can't be deleted. It's like deleting a program vs. the operating system.

According to the Wookieepedia entry on Protocol Droids each generation and unit was custom designed per task or customer who ordered it. It's very easy to assume that protocol droids were never designed for the intense lifestyle of the heroic figures C-3PO found himself associated with later in his life.

His fussy nature may have been a desired trait of his first owner. We can speculate all day on what his exact intended use was but all we know for sure is what we've seen and read about 3PO.

Answer 4

The non-in-universe answer is that George Lucas originally wanted C-3PO to be like a "used car salesman", but Anthony Daniels played the part as a "snooty English butler". Daniels' voice was supposed to be replaced by a voice-over actor, but Lucas eventually changed his mind and went with Daniels' idea. Daniels and Lucas said as much in the commentary tracks for A New Hope and Empire Strikes Back.

Other sources mention this fact:

George Lucas had not originally intended to use Anthony Daniels's voice for the voice of C-3PO. He only changed his mind after a suggestion by Stan Freberg, one of the actors considered as Daniels' replacement Daniels' voice was altered in post-production. His character was supposed to be like a "used-car salesman". Ultimately, though, George Lucas was won over by the charisma of Daniels' reading of the part as a "snooty British butler" and so Daniels has done the voice for C3PO ever since.

Source: Movie Buff

Lucas wanted C-3PO's face to be a completely neutral one that the viewer could read emotion into based on the droid's environment, and conceived of the character's personality as being akin to a used-car salesman who would say whatever was necessary to please others.

Rather than play C-3PO as a used-car salesman, Daniels channeled the voice of a fussy British butler, feeling that it fit the character's personality. Lucas briefly considered casting another actor to provide the droid's voice, but was convinced by sound designer Ben Burtt, among others, that Daniels's vocal performance was an excellent one that he had synchronized well with his body motions. Daniels thus re-recorded every line of C-3PO's dialogue. Burtt credits Daniels's complete performance as having created a total character.

Source: Wookieepedia

Interviewer: C-3PO was original written as sleazy used-car salesman-type of character, but on-screen he was more nervous than anything else. What brought that to the character?

Anthony Daniels: That was George's idea... he was always [sleazy] in the script, but it's how you interpret [the character]. That's the difference between actors. George never told me he wanted a sleazy guy. So I just looked at it. I had six months working with the script before we started filming because we were making the costumes, so I just interpreted it and George didn't have time to correct me. I'm afraid 3PO stayed the way he was. He is 3PO, he isn't me. He is this strange creation that came out of somewhere.

Source: Riverfront Times