After Anakin falls to the dark side of the Force and becomes Darth Vader, he takes R2-D2 with him when he goes to assassinate the Separatist council, but he tells him to stay with the ship.
He then gave both R2-D2 and C-3PO to Senator Organa, who in turn gave them to his ship captain, Captain Antilles, along with an order to wipe the memory of the overly chatty C-3PO.
After Skywalker turned to the dark side of the Force, the droid served Senator Bail Organa for a time in the Imperial Senate. Nineteen years following the purge of the Galactic Republic, R2-D2 played a pivotal role in helping the Rebel Alliance destroy the Empire's Death Star superweapon.
Darth Vader acts like he doesn't even know C-3PO or R2D2. They were with him since he was a child. He did everything he could to forget his past. Also, his plating had been replaced many times, and protocol droids all look very similar.
But Anakin remained staunchly against this idea for R2-D2, meaning the droid never had to worry about losing the memories of his past. As a result, R2-D2 could learn the value of intelligence, quick thinking and when and where not to speak up.
How R2-D2 Reacted to Anakin’s Fall to the Dark Side and Attack on Padme [Legends]
Did Vader recognize C-3PO?
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. because the Imperials thought he could hold valuable.
R2-D2 was present when Padmé gave birth to Leia and Luke, so he knew Luke was Anakin's son – but what he didn't know was that Anakin became Darth Vader. In addition to that, Anakin's fall was surely a painful event in R2-D2's life, one that he definitely wouldn't like to remember or even talk about.
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.
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.
The Invasion of Naboo. R2-D2 repairs the shield generator of Queen Amidala's Royal Starship. In 32 BBY, R2-D2 was in the possession of the Royal Engineers of Naboo, and was assigned aboard Queen Amidala's Royal Starship as a maintenance droid.
Throughout the three years of the Clone Wars, R2-D2 was Anakin's loyal helper and sidekick. In a daring rescue of Supreme Chancellor Palpatine, R2-D2 served as his master's assistant in his Jedi starfighter.
Towards the very start of George Lucas' creation of R2-D2, both he and C-3PO had speaking roles, leaving R2-D2's trademark bleeps without a place in the story. This plan was abandoned eventually, but C-3PO does often explain to the audience that R2-D2's bleeps often translate to swear words.
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.
However, R2-D2's memory is not wiped; as a result, R2-D2 is the only surviving character at the end of the saga who knows the entire story of the Skywalker family. Both R2-D2 and C-3PO end up in the possession of Captain Raymus Antilles (Rohan Nichol) onboard the Tantive IV.
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.
Either way, while Vader can use most other Force abilities, Force Lightning needs to be channeled, and Vader's limbs are explicitly not connected to the Force. The Star Wars: Episode III - Revenge of the Sith Visual Dictionary confirms Darth Vader cannot use Force Lightning, and even suggests this is the reason why.
The real reason why Obi-Wan Kenobi, the Lars family, or Darth Vader didn't act in the original Star Wars trilogy as though they knew C-3PO or R2-D2 previously is that the prequel trilogy, in which they first meet the two droids, had not been written yet.
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.
Although C-3PO is a tell-all, it's possible that he was directly programmed not to say who Leia is. This is something that George Lucas himself suggested in an interview back in the 1970s, which made it into the book The Making of Star Wars: The Definitive Story Behind the Original Film.
