C-3PO and R2-D2 are a severely underrated ship and that makes me sad, so here's a list of some things that I love about them:
-Bickering old married couple vibes
-Just how much they genuinely do love eachother despite how different they are
-Whenever Threepio puts his hand on Artoo's head or shoulder
-How happy they are to see eachother again in the Jawa Sandcrawler
-The "Hang on tight Artoo you've got to come back" and then the "You wouldn't want my life to get boring would you" bit in A New Hope
-When Artoo is badly damaged and Threepio is pleading with everyone to fix him. This is after they've been bickering the entire movie and now Threepio, notoriously selfish as he can be, is desperately offering up his own parts to save him
-That part in The Empire Strikes back where they're all preparing to flee the base on Hoff and Threepio runs over to Artoo and tells him to take care of Luke, but the bit that gets me is how softly he then adds "And do take care of yourself"
-Threepio gets so excited at the thought of Artoo being in Cloud City that he wanders off from the group because he thinks he hears him (and subsequently gets blown up RIP)
-After getting back to the ship on Cloud City, when they're in the middle of being pursued by the Empire, the VERY first thing Artoo does is start on putting Threepio back together. I just find it sweet because everyone else was too preoccupied to bother with him, (shoutout to Chewbacca for at least trying) but Artoo immediately goes to help him the first chance he gets. You get the sense that he's had to repair Threepio a lot, which is probably true and also very wholesome.
-Which reminds me of a similar scene in the prequels where Artoo appears out of nowhere in the middle of this huge battle and reattaches Threepio's head.
-That part in the droid torture chamber thing. Threepio is being taken away and shouts "Artoo don't leave me!" and upon seeing this Artoo proceeds to cuss out the droid that had him taken away lol
-I was gonna say all the times they rescue eachother but let's be real it's just Artoo saving Threepio.
-Artoo's little chuckle when everyone finds out that the ewoks see Threepio as a god
-When Luke uses the force to make Threepio float and Threepio calls out to Artoo for help, (like he'd be able to do anything even if he wasn't tied up lol). He's just too used to Artoo saving his dumbass lmao.
-I haven't watched much of the prequels but the first time they meet is adorable. Artoo is just like 'you're naked' and then they hang out for the remainder of Artoo's stay on Tatooine
-Double wedding at the end of Attack of the Clones (I'm kidding but the moment is still cute)
-That one time in the droids cartoon where Threepio is ready to physically attack this bigass robot because he thought it killed Artoo
-Then the moment afterwards when he sees that Artoo is alive and basically throws himself at him in a hug. "You foolish, wreckless... wonderfully brave little unit." 🥺
-The comic where Artoo hijacked a ship, flew to where Threepio was being held captive and went on a stormtrooper killing spree all by himself, just to save Threepio (because nobody else thought sending out a rescue party to save a droid was worth it 😤).
There's gotta be some more moments but I've only seen the original trilogy and bits and pieces of other Star Wars media here and there.
EDIT: I've remembered a few other moments so here we go
-When Luke is flying to Cloud City to save his friends Artoo says something to him and Luke replies with "No 3PO's with them". So he presumably said something along the lines of 'What about Threepio? or 'Did they leave Threepio behind?' or maybe he was asking if Luke could sense if Threepio was okay. I just love how they add little details like that. They didn't need to include it at all but it's moments like this that really flesh them out as characters by showing how much they worry about eachother.
-In Attack of the Clones, when Threepio is on that conveyor belt thing in the droid factory, instead of worrying about his own safety he's like 'Hmm. I wonder what happened to poor little R2'. Like boy you've got bigger problems right now, not to mention the fact that Artoo pushed you off the edge in the first place lmao
-Lego Star Wars: Droid Tales has quite a few moments. The whole plot is Threepio trying to find and rescue a kidnapped Artoo (the tables have turned for once omg!) And he's so determined to save him it's so cute.
-Lego Artoo carries around a copy of Threepio's memory with him.
-Lego Threepio pulls a photo of Artoo out of nowhere then proceeds to gaze longingly at it, lamenting over whether he'll ever see him again.
-Admiral Ackbar is reminiscing over his stolen ship the same time Threepio is trying to talk about Artoo, so Threepio goes 'A ship is just a machine. A droid is a person...' and idk I just love the way he says it.
-There's a flashback to the end of the Empire Strikes back and Threepio is like 'R2 I thought you were lost for good. I am so happy to see you again!' And he's so excited it's so cute.