As anyone who has flipped through Vogue or Harper's Bazaar in recent years can attest, it's quite a challenge to find models who don't look dour and perplexed, as though they've just gone through painful psychotherapy or mistaken whole milk for skim. The fashion business, for all its outward absurdity, isn't cheeky and good-humored at its core, and that is perhaps why Isaac Mizrahi made such an impression.
In an era when most big designers aren't necessarily known for wit or verbal agility, Mizrahi emerged in TV interviews, and especially in the acclaimed 1995 documentary about him, Unzipped, as a...