Din Djarin wanted IG-11 to accompany him to Mandalore but he ends up taking R5-D4, an alarmable astromech droid that has a slightly significant history in the Star Wars universe.
Din travels to Mos Eisley to get Peli’s help in acquiring a memory circuit for IG-11. She asks Jawas who are in a workshop at the time but they say they don’t have the part.
She then suggests her own astromech droid, R5-D4, as the perfect companion on his trip. When the droid expresses concern, Peli threatens to sell it back to Jawas where it might end up being stripped for parts.
She convinces Din to take the droid off her hands but R5 is not just another random droid to appear in the Star Wars universe and has shown up in a surprisingly key moment before.
Indirect savior of the galaxy
Long before the astromech was traveling around with Peli, R5 served under a master on Tatooine, back when Anakin Skywalker was still a Jedi Knight. He was then a part of the early rebellion before being picked up by Jawas.
The Jawas were ready to sell R5 but he was convinced by R2-D2 to sabotage himself so the Jawas had no choice but to sell R2-D2 to any prospective buyers. R2-D2 was at the time, carrying the stolen plans of the Death Star and was ultimately bought by Owen Lars and Luke Skywalker.
R5-D4 was almost picked up by the Lars family before he begrudgingly listened to R2’s claims that the fate of the galaxy was dependent on the blue and white astromech being bought instead.