The Ugnaught mentions a Mythosaur. The Mandalorian symbol seen decorating their headquarters is based on the skull of this fabled beast and is called "Kyr'bes" in Mando'a.
The Blurrg creature first appeared on screen in Ewoks: The Battle for Endor (1985). They were based on unused concept art by Phil Tippett originally developed for the Tauntauns from Star Wars: Episode V - The Empire Strikes Back (1980). Blurrgs were seen again on the planet Ryloth in Star Wars: The Clone Wars (2008) episode Liberty on Ryloth (2009) and the Star Wars: Rebels (2014) episode Hera's Heroes (2016).
Dr. Pershing (Omid Abtahi) wears a patch on his right arm with the Clone Army Project emblem that was first seen on clothing worn by the Clones training on Kamino in Star Wars: Episode II - Attack of the Clones (2002).
The Ferryman (Chris Bartlett) is of the Kubaz species, the same as the snitch Garindan seen in Mos Eisley in Star Wars: Episode IV - A New Hope (1977). Part of the same vocal sound effects from the original film are reused. According to sound designer Ben Burtt, he fabricated these sounds using electronic buzzing from a synthesizer mixed with sped up and processed audio performed by actor John Wayne.
The first season's price tag was in excess of $100 million. This works out at an average of $15 million for each episode, though some of those costs would be amortized due to them being for costumes, sets, props, puppets and digital creations that would be used throughout the series.