The simple way is play using the creature who's mind you want to use, quit normally.
Next look in your creature minds folder and copy the last updated ???????.erc file, say to the desktop with a new name like "PET".
This will give you a copy of the mind you want.
Next again this is an easy way to do it but it works for this demo.
Download and install "Surviver" by "Lunar" you should spot it in the DL section.
In the actual map text viewed in say notepad you will see "COMPUTERCONTROLLEDCREATURE" replace this with "PET".
Then place the "PET" file in the same folder as "COMPUTERCONTROLLEDCREATURE" yes it is a long way round this way but the mechanics should be clear.