Back before there were Red Hulks and Gray Hulks and Orange Hulks, She-Hulk was the first heroine to spawn from Bruce Banner's gamma-irradiated blood. Jennifer Walters is cousin to Banner, and when she was grievously wounded, Banner was the one to supply her with a life-saving transfusion of blood. The side-effect was that Walters gained the ability to transform into a Hulk herself.
While initially She-Hulk was every bit as savage as her cousin, she quickly evolved into a far different character. For this Hulk, the transformation isn't about unleashing anger but removing inhibitions and enjoying life. Jennifer Walters is a shy, mousy woman who focuses too much on her career and not enough on her personal life. She-Hulk is bold, vibrant, and not afraid to have fun. Not to mention strong enough to make just about any villain think twice about threatening New York. The challenge for Walters has always been reconciling the two sides of her personality into a manageable whole. That struggle sets her apart even as the number of Hulks has skyrocketed in recent years.