I’m gonna do my best because it doesn’t really have a set definition. Jenny Thunder is basically an homaage to all pre-spn, mostly modeling phase young Jensen when he was a strapping young actor/model. I think it amusingly comes from J-Lo’s “I’m still Jenny from the block” wherein Jensen has come a far way but he is still, Jenny from the block aka the young twink model he started as. I basically tag “Jenny Thunder” with any pictures of pre-spn (aka pre 2005) pictures of him and to me it’s more of a “bby jensen” tag. BUT there are whole blogs devoted to his modeling and silliness of his youth which are specifically “Jenny Thunder” blogs. I’m trying to remember where the “thunder” came from. I think it might be like be attributed to an old weight loss thing, I used to know but damned if I can remember it right now. But that is the basic premise.