Iris Alonzo was reflecting, with mock regret, on the success of the deep V-neck T-shirt she helped create for American Apparel years ago.

“I single-handedly destroyed West Hollywood,” she said. “You’d roll up to La Cienega and Santa Monica Boulevard and there’d be a guy with a shaved chest and his shirt pulled down to his belly button. ‘Oh, my God. What have we done?’”

Ms. Alonzo, at 37 perhaps the most influential former senior creative director you have never heard of, was sitting in a friend’s apartment just off Central Park West, talking about her decadelong career with the brand that turned the T-shirt ad into an R-rated experience, before filing for bankruptcy last year.