Healthy Hair Tip: Make sure hair is COMPLETELY dry before using a curling/flat iron. The Journal of Cosmetic Science has some pretty horrible pictures of what happens to the hair cuticle if you use a hot tool when hair is wet. The cuticle gets cracked, split and blisters up. And once you do damage like that, there's no fixing it. Be careful, kittens!
On the left is a healthy hair strand. On the right is a damaged hair strand. The cuticle is lifted and shattered. This is similar to the photo of what hair looks like after curling hair when wet.
Image: Google Images
References: Journal of Cosmetic Science: Effects of thermal treatments with a curling iron on hair fiber

So this old wive's tale got brought up today and I thought I'd set the record straight: pulling a gray hair out will NOT make more gray hairs grow! The hair follicle only has room for one hair. brought up a very valid point: if this were true, don't you think people who were balding would just sit around plucking the hairs that were left to produce more hair and never go bald? Going gray is usually determined by your genes. However, there other things that can contribute to when you start going gray: anemia, thyroid issues and smoking to name a few. But plucking them will not make matters worse, so don't hesitate to pluck a gray hair!

Image: Google Images