Rex is Bobby's dog who became feral due to disease. Bobby hid Rex in the Agriculture Center's cave hoping that he would recover over time, fearing that it will be put down otherwise.
- Rex will appear in the cave and has to be fought. "Rabid Dog" is Rex's more powerful form which spawns if the cave remains in darkness. A weaker variation, Spiked Mut will appear if a match is lit upon entering the cave.
- If Rex is killed, Bobby digs a grave for it and will not forgive the Rangers for their allegedly heinous crime.