As I remember in looking at the early (Kirby) issues of the Hulk comic, Dr. Banner wasn't a "total square." He wore purple pants with cuffs. Not daring, as he was otherwise dressed like a good researcher of the day would have. Blues, grays, browns and greens, were also common colors for pants. But dark purple slacks were not unseen. They could have been something like pleated work slacks from Sears. Those slacks had hip pleats. I know that when you snap off the belting fabric you still only gain about two to four inches at the hips and no inseam. And as the joke goes, "If my pants were that tight, I'd turn green too."
OK, so we give Bruce pleated work slacks with Inseam Guard (1966?) and almost no wear. Brand new! That might let the fabric stretch out to paper thin for a while. Is the tension itself holding the stitching in place? Is the fly fused shut?
Looks like some questions breed more questions.