^I don't know if it's JUST that they look like lab rats. It's very possible that's where a lot of the original stock came from. Labs still sell animals for lab use, but over bred animals will need to be used for something. Very easily could have been rodents sold to zoos and private collector herpetologists who basically set these lab rats as the standard for what rodents we use as feeders. We think of them as sterile and used for lab purposes, probably cause most are. Not to mention--where else in the early days would you find clean, captive bred rodents that people would NOT be mad that you fed to a snake. I think a lot of the rats used in feeding and pets have their origins partially thanks to these people...Heck, that's how we got axolotls. A lot of people bought excess from laboratories. Decided they were cool pets!