Though the characters had technically larger roles, the creatures and droids within Jabba's Palace really made it what it became, as they gave the palace its distinctive look and feel.
It's really not Jabba's Palace if the iconic Kowakian monkey-lizard, Salacious Crumb, isn't there. Though his only real purpose was to nest in the crook of Jabba's tail and scream-laugh at the visitors who stopped by, Crumb has become one of the most beloved creatures at the palace.
The Max Rebo Band
Who's better at bringing overall good vibes than the man himself, Max Rebo? This lovable, squishy-looking Ortolan helmed the band of his same name, which played an assortment of jazz for everyone who hung out at the palace.
Sy Snootles (what a name) performed with the Max Rebo Band in her unforgettable performance at the palace, singing the song, "Lapti Nek," a Star Wars classic that is currently stuck in my head.
Yowza, a Yuzzum, was also featured in the performance of "Lapti Nek," for which he provided some additional vocals in the updated version of the film.
Pateesa, the Rancor
A lovely creature that lives beneath the trap door in Jabba's Palace, the massive rancor takes down every victim that's dropped down to him without a second thought. I do have to say that one of the saddest moments of Star Wars is seeing his trainer, Malakili, so incredibly sad after it's killed in Return of the Jedi.
Gamorreans are practically synonymous with Jabba's Palace—they're the brute strength of the bunch and guard the palace, though they can be fairly clumsy sometimes, like when one of them fell down the trap door in Return of the Jedi.
This creature was a weird, bulldog-looking frog with a spiked collar who served as a guard dog for the palace. Though it didn't seem like he was really doing much, he was actually a trained assassin who worked with the Imperials.
BT-16 Perimeter Droid
The first droid we encounter at Jabba's Palace in Return of the Jedi, the BT-16 Perimeter Droid hilariously scares C-3P0 as he's walking in. These droids primarily acted as forms of security as they walked the halls of the palace and were equipped with different sensors and blaster cannons. In The Book of Boba Fett, we see this droid walking around outside of the palace as security, as well.
EV-9D9 and 8D8
EV-9D9 controlled the torture chamber of the palace, where she took apart various droids and tortured them, though she was just hired as a mechanic to deal with the droids that came and went. She worked alongside 8D8, another droid who dealt more so with the Gonk droids, which he also tortured. Overall bad vibes here. However, he ends up working for Fett in The Book of Boba Fett, serving as the majordomo of the palace.