A cake for each birthday person. Jonathan Ziegler/PatrickMcMullan


The invitation featured a school of fish trailing a merman with hair made of coral riding a sea horse. It said that the evening was "to celebrate all things Pisces." "It's a tradition," said Mr. Demsey. "And it gets fishier every year."

The three celebrating Pisces: Alina Cho, John Demsey and Marilyn Gauthier. Natalie Keyssar for The Wall Street Journal

Aerin Lauder and Donald Robertson Jonathan Ziegler/PatrickMcMullan

Thom Browne Jonathan Ziegler/PatrickMcMullan

There was lots of fish bric-a-brac brought in for the evening. There were fish sculptures, ceramic fish dishes, sugar cookies in the shape of fish and red Swedish fish. A video of fish swimming played for the duration of the party which particularly excited Mr. Demsey's young daughter, Marie-Helene.

There were a lot of people at this party. If one wanted to continue the metaphor, one could even say it was as busy as the bottom of the ocean, at least as presented by "The Little Mermaid" and "Finding Nemo."

"I was told this was a sit-down dinner for 20 people," one guest remarked, sarcastically.

More like 400 of their nearest and dearest. "Yes, people must not really like them at all," said Pamela Gross Finkelstein, surveying the extensive crowd, which included Jerry Della Femina and Judy Licht, Aerin Lauder, Glenda Bailey and Ellen von Unwerth.

There are some downsides, apparently, to throwing a Pisces party. Ms. Cho, who is quite active on the social circuit, said that last year, "I got all of these fish gifts." She went on: "I got fish platters. I got fish key chains. I got a Swarovski coin purse in the shape of a fish. I don't quite know how you tell people, 'No fish gifts.' "

Leaving Mr. Demsey's townhouse, it seemed appropriate to call an astrologer and find out why a Pisces party might attract such a crowd.

"No one has ever asked me this question before," said Susan Miller, late on Thursday evening. She is known for her work with the zodiac and her website Astrology Zone. "But Pisces fit into New York so well. It's a sign that loves the arts, that needs to be creative. If a Pisces doesn't let out the creativity, they're unhappy. New York embraces and celebrates creativity. It really is the perfect place for them."

Ms. Miller added that, traditionally, Pisces "like to be alone but they also like to be with people. There's a part of them that's shy and modest. But right now, Pisces are making lots of friends and new associations because the eclipses are bringing people to them. It's almost like they're shedding those little gills and new ones are growing." (Some notable Pisces, besides the aforementioned: Cindy Crawford, Sharon Stone, Eva Mendes, Jessica Biel and Bret Michaels.)

Ms. Miller wanted to make sure to offer some projections for Pisces for the coming months. She said that, since 2007, the sign has been experiencing its "most difficult time." "There was some disillusionment with people around them, their health wasn't good, and this was not a robust time. But they're celebrating now because they're free at last."

On June 4, she said, "when Jupiter goes into Taurus, you're going to hear about Pisces writing screenplays, poetry, creating choreography. This phase will go all the way to June 12, 2012. They're going to have tons of money and go through periods of drought, but they're going to want to make sure they have good accountants."

Apparently the next year will also be a good time for the Pisces private life. "They've been really out there worried about their career, but now they'll have time to devote to personal life. They have a really nice forecast."

Ms. Miller also had some insight unrelated to the Pisces sign. Completely unprompted, it was about the Broadway musical "Spiderman: Turn Off the Dark." "They're doing everything inside out, they're doing it while Mercury's done retrograting!"

"They're now opening on the total eclipse of the moon," Ms. Miller said. "They couldn't pick a worse day. And I looked up Julie Taymor's chart [Sagittarius]. Things do not look good—you don't even want to know."

"I wish I could help them," Ms. Miller added. "They're totally out of sync."

Write to Marshall Heyman at marshall.heyman@wsj.com