This being the weekend before Halloween, Frankie Stein is busy.

Yes, that's her name. And costume designing and rentals are her game.

Her colorful store, called Frankie Steinz (entrance is by appointment only) can be found on a side street in New York's trendy Tribeca neighborhood, not far from Robert De Niro's apartment.

Stars have relied on Stein's costumes for years, since her days of running a specialty store in Aspen, where she catered to the likes of Jack Nicholson ("He was always buying for Anjelica Huston, who was his girlfriend at the time") and Goldie Hawn ("For her children's parties"). She also once dressed up John Denver as Kermit the Frog.

"My business is mostly by word of mouth," Stein, 47, told PEOPLE.com on Thursday as the head of Mr. Smee from "Peter Pan" gazed over her shoulder. Marilyn Monroe, Joan Crawford and "My Fair Lady" dresses for Audrey Hepburn hung overhead.

"I'm actually a trained CPA," said Stein, dressed in a black pantsuit. "I got into this by moonlighting."

Stein moved to New York 14 years ago. Five years ago she assisted Billy Joel and others in preparing for Elton John's 50th birthday costume party. She also helps outfit Aerosmith for their tours.

Throughout the past year she has dressed Rosie O'Donnell ("She wanted to be Snow White") and the women on TV's "The View." "Star (Jones) was Cruella de Ville." And last Halloween she helped actress Jennifer Grant -- daughter of Cary Grant and Dyan Cannon -- with her costume. "She was grapes," Stein said, straight-faced.

The costumes rent for anywhere from between $95 to $225 and, typically, says Stein, "the stars come at the last minute, in limos, at night."