So, who sez big stars never have any normal, upscale, stylish fun and nobody in “show biz” ever gives a party anymore unless it’s “promotional.” Turns out not to be true.

Last week, at the posh St. Regis Roof in Manhattan, those married lovebirds Catherine Zeta-Jones and Michael Douglas gave themselves (and others, famously born on Sept. 25, such as Barbara Walters and Will Smith) a birthday party to end all. Catherine was glorious in her svelte dark red satin gown and Michael was as handsome as ever in his dynastic, civilized manner. (Michael is one of the rare Hollywood offspring to do his forebear, Kirk Douglas, proud.)

Michael kicked off the dinner with a brief welcoming speech and salute to his young bride, and she took the microphone to introduce a number of tables of her relatives and pals from Wales. They all stood and sang us a Welsh song.

Soon to star as Desiree in the revival of Stephen Sondheim’s “A Little Night Music,” Catherine shuddered when I asked if she had ever seen this famous classic cult musical? “No, and I’m scared to death!” said she, throwing up her hands. But as she won an Oscar for the movie version of “Chicago,” I’m sure she has nothing to worry about.

Michael said they are very happy having moved to New York for the near future and he has just started his sequel to 1987’s “Wall Street,” where he will revive the character Gordon Gekko. “Greed, greed, greed ... good, good, good!” he laughed.

I had a nice exchange with the birthday couple’s young son Dylan, age 9. I told him I had seen his beautiful family house in Bermuda and he said, “Yes, we love it there. It’s great.” Dylan is very grown up!

Donald Trump said to his beautiful Melania, “Do you know how many years I have known this woman?” indicating me. Melania sighed: “Yes, Donald, I know. You tell me this same thing every time we see Liz.” I had a lot of fun dishing with Donald over the fabulous St. Regis lamb chops. He loves gossip and I do too. He is a fascinating dinner companion. (And to think, back when the book “Lost Tycoon” came out, Donald and I were shown as enemies in the pages.) Wise people change their minds!