It began as a "Zoolander" spoof, but the New York couple who launched a Tumblr that showed their dog dressed in preppy clothes say it's become a big business for their fur-covered menswear model.

The lights dimmed. The music swelled. The audience began to clap and cheer as they stared at the runway in anticipation. Then suddenly, a puppy scampered onto the stage and the show began. About 25 ...