Ever since “Ghosts” premiered in October, viewers of the CBS sitcom have been wanting to know why Trevor, played by Asher Grodman, doesn’t wear pants. Even costume designer Carmen Alie has been stumped.

“I was wondering how he died,” Alie says.

The episode airing March 31 will reveal how Trevor - a former Wall Street trader from the ’90s who’s one of the several ghosts haunting an old house in New York’s Hudson Valley - met his demise. But more important, it will explain his mysterious lack of trousers.

The episode involved a flashback, and Alie turned to “The Wolf of Wall Street” for inspiration, knowing she would have to show Trevor and his Wall Street bros on the trading floor. That meant a flood of gray and navy suits. “But the detail was different back then,” Alie points out. “The width of the stripes - one inch apart - you don’t see those anymore. Also, I had to look at the width of the lapel because that too was different,” she says.

Alie searched high and low for thicker fabrics and eventually found a wholesale place to fabricate the suits. “I made each one tailored to their personality,” Alie says of Trevor’s work colleagues. Her goal was to maintain the idea that Trevor was cool and chic while alive. “The navy blue [of his blazer] was very business-looking. His shirt was this great combination of blue with a white collar, and his tie - of course, we needed more than one - was by a French designer,” Alie says.

Production designer Zoe Sakellaropoulo found an abandoned building to bring Trevor’s Wall Street world to life. “I love what Carmen did with the gray and navy suits, and we came in and added this white, gray, black and wood furniture to represent that dry world,” says Sakellaropoulo, who filled the set with desks, chairs, a trading wall and monitors. “It was a male-dominated culture, and we wanted to show that.”

As the flashback reveals, Trevor’s sense of altruism ends up affecting his wardrobe in the afterlife. But for one episode, at least, he gets to dress up. “I always had his pants handy,” Alie teases.

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