Nope, not that I can tell. I've found that any that I've had that were mellow from day one have remained that way, especially if held on a regular basis. My amel was like that, my lav and some of the Okeetees. My one Okeetee female was a complete terror as a baby so I left her strictly alone except for necessary handling. Around 18 months old, she suddenly calmed down and is now one of my most calm snakes. It's not necessarily bred in either. One of the offspring of one of my mellowest Okeetees is a pure terror. Thinks he's a rattlesnake (rather cute actually) and some of the mellowest babies are Tepin's offspring. She was the terror when she was younger. Each morph has mellow ones and crazy ones. I usually suggest first time buyers either go to a show or to the breeder's house in order to be able to handle the snakes themselves. I think it's better to get one that may not be as pretty, but is more laid back. They eat better, stress less and generally are easier to deal with. If I'd had Tepin instead of C.S. as a first snake, I might have sworn off corns forever!