Varnias Tybalt said:
Still doesn't explain the "bastard" characters that tend to sneak in the game. Even the DnD miniatures have bastard species such as Lizardman/Ilithid and other species-transcending wierdness. (I actually have one of those in a cardboard box somewhere
)
The lizardman-illithid would probably be a result of the illithid breeding process, which involves implanting an illithid larva into the brain of a host. The larva take over the body, which slowly transforms into an illithid. Technically all illithids are 'bastards', a bonding of illithid and another species.
As for the other races (half-elf, half-orc etc), why not?