Solo: A Star Wars Story introduced us to the first droid in the history of the franchise that was concerned with the well-being and equal rights of their fellow droids. L3-37 (voiced by Phoebe Waller-Bridge) is Lando Calrissian's co-pilot on the Millenium Falcon and has "the best damn navigational system in the galaxy," according to Calrissian (Donald Glover). There's also a hint of a love affair between the two characters.
Unfortunately, her crusade to attain equal status for droids proves to be L3's downfall when she sparks a mass breakout on Kessel. She is fatally shot and Lando is forced to rip out a core piece of her machinery and plug it straight into the Falcon's computer, allowing Han to complete the Kessel Run in less than 12 parsecs with an alternate route away from an Imperial blockade and through the dangerous maelstrom.
Nevertheless, she's a part of the iconic ship from that point on and thanks to a recent Throwback Thursday tweet from the official Star Wars Twitter account, it looks like L3 has been retconned into the original trilogy. The tweet involves a picture of C-3PO (Anthony Daniels) from The Empire Strikes Back when, on the Falcon, he says to Han:
"I don't know where your ship learned to communicate, but it has the most peculiar dialect."
3PO says this after interacting with the ship while Han and Chewie attempt to fix the hyperdrive. He, being so anxious and nebbishy all the time, would obviously find L3's free-spirited and rebellious nature "peculiar." 3PO is a protocol droid, which are a dime a dozen and created to follow orders, whereas L3 does her own thing; her own, self-made directive to lash out against their creators is in direct opposition of his own.
Lawrence Kasdan, who helped write both Solo and Empire, probably thought it would be a fun idea to tie the two films together by offering an explanation of the personality behind the most famous starship in the Star Wars mythos.
Of course, L3 most likely wasn't invented until he began writing the Solo script back in 2012, which means she's a bit of retoactive continuity, but it's still cool to see the creative team behind the franchise actively looking to connect even the smallest of plot points.
Funnily enough, the theory that the movie would reveal the "identity" behind the Millenium Falcon in the form of L3 was being put forth as far back as March, when Screen Rant laid out a pretty convincing case in depth. Looks like they were right all along with the above-mentioned tweet serving as the proof in the galactic pudding.