Callahan is a deer hybrid. His lower half is that of a deer. He has soft brown hair that is a little messy. He has a pair of short antlers on his head as well as deer ears that tend to twitch to betray his emotions. Callahan is mute and tends to use sign language to speak to those around him. An old injury has led to him being unable to speak. Callahan tends to be rather introverted but opens up when people he trusts are near. He likes joking with his friends when able to.