|File:Rabbit EVO profile.png|
|Unusual features||Eyes on jaw|
|Special abilities|| Enhanced stamina|
|First appearance||"Operation: Wingman"|
The Rabbit E.V.O. is a very dangerous, large, mutant rabbit. More than one has appeared throughout the series.
Operation: Wingman The Rabbit E.V.O. first appeared near a rural road in the desert. After Rex insulted it, the rabbit started to relentlessly chase after Rex, trying to kill him. Even while in the midst of going on a double date with one of his best friends, Noah, the rabbit still attempted to chase him. After a long night of chasing Rex, it was finally defeated with a heat seeking missile.
Later, a second Rabbit E.V.O. was captured and added to the ranks of the Petting Zoo. After Dr. Holiday spent time with the E.V.O. and conducted research, it is later revealed that the cause of the rabbit's earlier rampage was that it was a starving pregnant mother about to give birth. She, her children, and the other inhabitants of the Petting Zoo nearly escaped when Robo Bobo released them as part of the "ultimate practical joke". Their escape was prevented only by the arrival of the real Bobo Haha. This rabbit appeared to have a calmer bond with Dr. Holiday. 
- Strangely, this rabbit E.V.O. had 6 legs/arms but its offspring had only 4.
- The Rabbit E.V.O. seems to be based off the movie Monty Python and the Holy Grail killer rabbit which was able to fight off and kill four knights with little difficulty.
- The Rabbit E.V.O. appeared twice in the game Generator Rex: Agent of Providence. The first time was as the boss of the Amazon level where after a prolonged fight Rex fought it off and released it back into the Amazon, not killing it because he had other things to attend to at the time. Following this Breach sucked the rabbit into her pocket dimension where Rex fought it again as the mini-boss of the Greenville level.