The Redzs are based on Tyrannosauruses, although they are much smaller, relatively stocky and resembles more Velociraptors. They have a red round body, tail and head with short and thick gray legs, orange two-clawed feet, short red arms with two-clawed hands, black eyes, and a gray jaw with sharp teeth.
Originally, Redzs were going to appear in the Hidden Palace Zone, but the Zone and its Badniks were both cut from the final game. Regardless, the Redzs could still be found in the Nick Arcade and Simon Wai prototypes. Here, their attack pattern is very similar to the Moto Bugs' - they do not attack and can be destroyed easily.
In the 2013 re-release of Sonic the Hedgehog 2 which restored Hidden Palace Zone, the Redzs made their official debut. In this version, they will stop if they spot the player and spit a short stream of flames from their mouth. However, in Proto Palace Zone, the Redzs retain their original attack pattern.
Redz, or a similar enemy, is also called Tyrannysaurus Rex in early design documents. It is unknown if this is an intentional play on words or a spelling error.
In the Nick Arcade and Simon Wai prototypes of Sonic the Hedgehog 2, the Redz along with the BBat are the only Badniks in the game to reappear on-screen after they have been destroyed if the player returns to the said Badnik's location.
The Redz appears as the icon for the "A Secret Revealed" achievement.
The design document listing the Redz enemy as "Tyrannysaurus Rex".