Brian Lee knows how to create companies with star power. Just eight months after he teamed up with Jessica Alba to start The Honest Company, a maker of baby products, Lee has partnered with Jennifer Lopez to launch, a Los Angeles-based T-shirt company.

"I'm coming up with new ideas all the time," says Lee, who also co-founded ShoeDazzle with Kim Kardashian, as well as "It's a blessing and a curse."

For Teeology, Lee's idea was to incorporate crowdsourcing. Artists submit designs, which are curated by Lopez and the Teeology team. Then, customers vote online for their favorites. The designs with the most votes get made in limited quantities and sell for about $29.

Lee approached Lopez because of her role on American Idol. Increasingly, however, he is the one receiving calls from stars who want to leverage their fame in entrepreneurial ways. It's thrilling, he says, but juggling four start-ups keeps Lee pretty busy.

"I'm kind of dying for a few days where I don't do anything," he says.