The lack of recognition could have come from an old man simply not remembering the passing droids of his youth. Lastly, Owen didn't seem the sentimental type to form any emotional attachments to droids. Being a practical man, he viewed them as tools to be used and replaced when they no longer functioned.
C3PO was clearly created from some sort of kit or existing prototype since every protocol droid aside from coloring looks the same. He didn't recognize him because again, they all look the same & it was decades until he saw him again. There was no reason to believe he or R2 even existed anymore.
Bail's final line of the film and instruction to the Captain, says “…have the Protocol droid's mind wiped.” Because Bail Organa had them wipe his memory at the end of Revenge Of The Sith and he never came back to Tatooine until A New Hope.
Obi-wan responds to starwars.wikia.com/wiki/Luke_Skywalker saying R2 belongs to him with, “I don't seem to remember ever owning a droid,” which is technically true, because Obi-Wan never did “own” R2 or C-3PO. Obi-Wan then makes a comment that suggests he's more than aware of R2's impressive capabilities.
C-3PO had his memories wiped after Episode III, but R2-D2 did not. However, they were working together on the same ship afterwards, where presumably, they would have conversations.
With the fate of the galaxy hanging in the balance, C-3PO reluctantly agreed to have his memory erased so the runes could be read. Fortunately, this mechanical amnesia was only temporary, as R2-D2 had backed up his friend's memories before C-3PO left.
Since Bail Organa had C-3PO's memory wiped previously in order to prevent him from spilling the secret of Leia's parentage, it could be that this was a semi-regular occurrence for the droid given he couldn't be trusted to keep quiet about things.
Darth Vader's true identity as Anakin Skywalker was a highly guarded secret, known only to a select few individuals including Palpatine, Obi-Wan Kenobi, Luke, Han, Leia, R2-D2, C-3PO, Master Yoda, Bail Organa, Ahsoka Tano, Darth Maul, Grand Moff Tarkin, Grand Admiral Thrawn, Jocasta Nu, Ferren Barr, Verla, Reva, ...
secondly, in Legends, R2 was given programming that actually restricted him. from sharing any information with Luke or Leia. about their parents or relation to one another. this was all part of the plan. to conceal this information from the twins.
She senses Anakin when she reaches out to the pilot — and Vader realizes that Ahsoka, his former Padawan, lives on. In Season 2, Episode 18, “Shroud of Darkness,” Ahsoka's guilt manifests as a vision of Anakin, who's angry with her for leaving him all those years ago.
As evidenced in the world of Star Wars, the galaxy is chock full of 3PO series protocol droids, making the odds of C-3PO being the same droid that worked on the farm decades ago incredibly slim. Owen could have easily assumed that these were two different protocol droids if he didn't put much thought into it.
While this issue provides evidence that Chewbacca hates C-3PO, Chewie seemed to get all of that pent-up rage out of his system when he gave Triple-Zero a proper beat-down.
The sequence calls back to a similar scene in Revenge of the Sith, when Bail Organa orders Threepio's memory be erased to prevent him from sharing information about Anakin Skywalker's fall to the dark side.
They aren't abbreviations — they're model and serial numbers. R2 is a second generation R-series astromech, serial number D2. * And C-3PO is a C-series protocol droid with the serial number 3PO.
Unfortunately, Rex and Vader never meet again though. Why didn't Palpatine feel afraid of showing his evil actions, behaviors and ways to Anakin and the Jedi anymore?
Star Wars Theory: R2-D2 Didn't Know Anakin Skywalker Became Darth Vader. R2-D2 served Queen Amidala and later Anakin Skywalker, accompanied by C-3PO. Unlike the golden protocol droid, R2-D2 never had a full memory wipe, so he was well aware of all events that happened around him.
Since Obi-Wan and Anakin often fought together, Obi-Wan was friends with R2-D2 as well. This means that although R2-D2 might not have immediately recognized Obi-Wan on Tatooine due to his age, Obi-Wan should have recognized the droid.
in the Dark Horse comic series star Wars Tales, which is now part of legends, it's revealed that Darth Vader did recognize C. 3PO on Cloud City. when 3PO was shot by Stormtroopers, his parts were brought before Vader.
Weaknesses: C-3PO is not a combat droid in any capacity, and dislikes fighting. His protocol droid body is stiff, slow, clumsy, and built for aesthetics rather than function. He is quite cowardly and usually surrenders at the first opportunity.
As a young boy, Anakin Skywalker constructed C-3PO to assist his mother, Shmi, on their home planet of Tatooine. When Qui-Gon Jinn, Obi-Wan Kenobi, and Padmé Amidala encountered Anakin while stranded on the planet, C-3PO met R2-D2, an astromech droid owned by Padmé.
C-3PO was a recreation of Anakin Skywalker after he was found in the dunes of Tatooine by Anakin and a fellow slave friend. He later became in possession of Anakin's wife, Padmé and then their children, Luke and Leia. C-3PO and R2 were the only ones who knew Anakin and Padmé were married.
