Mayor Thomas Menino has proclaimed today Curious George Day in Boston. This is one thing Maura Hennigan would likely agree with him on. What's there not to like? Curious George is the Johnny Damon of children's literature: fun-loving, hairy, always on the go.

The reason for the proclamation is that today is the 64th birthday of everyone's favorite mischievous monkey. The event will be celebrated from 1 to 4 p.m. at the Boston Public Library in Copley Square. More specifically, it will be celebrated in the Rey Children's Room, which is named in honor of Margret and H.A. Rey, Curious George's creators. George and his friend The Man in the Yellow Hat will be on hand, as will chef Ming Tsai (who'll be offering up birthday cake at 2:30 p.m.) and children's book author Louise Borden. Borden's latest book is ''The Journey That Saved Curious George: The True Wartime Escape of Margret and H.A. Rey." It chronicles how the Reys fled the Nazi invasion of France in 1940, and how they came to the United States.

The Reys wrote and illustrated seven Curious George books, and another 20 have been done by other hands. Few characters can match George for popularity. His books have sold 30 million copies and been translated into 16 languages. In February, a feature-length cartoon will be released, with Will Ferrell as the voice of The Man in the Yellow Hat. And PBS plans to start broadcasting a Curious George cartoon series in fall 2006.

''Everyone knows who Curious George is and loves the character," Borden said Thursday over tea at the Lenox. ''Now I hope they'll fall in love with Margret and H.A. Rey and find out who they were, too."

They were born Hans Reyerbach and Margarete Waldstein -- he in 1898, she in 1906. Both were artistically inclined (she even studied at the Bauhaus), and both ended up in Brazil, where they met. They there married in 1935.

Hans and Margarete moved to Paris. They started to collaborate on children's books. One of their characters was a monkey named Fifi who bears more than a curious resemblance to you-know-who. They also shortened their name to ''Rey," and Margarete became ''Margret." Then came World War II. As German-Jewish emigres, the Reys were in grave danger once the Nazis conquered France.

How they got from Paris to America was the subject of a magazine article that caught Borden's eye in 1995. The story intrigued her for two reasons. Growing up, she hadn't read the Curious George books, but her three children had all been fans. And Borden had just finished a children's book on the evacuation of Dunkirk, so the fall of France was much on her mind.

''I had this image in my head of them in this sea of humanity coursing south from Paris," Borden said. ''I couldn't find books or stories about them, so I said, 'I'm going to write this myself.' "

Borden began a series of investigations that would take a decade, cover three continents, and result in her 20th book. She followed the path of the Reys, from Paris to Normandy, then down to southeastern France, through Spain to Portugal, back to Brazil, and, finally, to the United States. Borden, 55, is an Ohio native and lives in suburban Cincinnati. She and her husband lived in Natick in the early '70s. He taught history at River Country Day School, in Weston; she was an assistant first-grade teacher at the Meadowbrook School, also in Weston.

After they moved back to Ohio, Borden gave up teaching to stay home and raise their children. When the children got older, she began working in a neighborhood bookstore and writing for children. Her first book was published in 1987. She writes both nonfiction and historical fiction.

''The Journey That Saved Curious George" almost qualifies as both: It's a true story (Borden, a demon for research, visited all the hotels the Reys stayed at in France), but it reads like fiction, right down to the Reys cycling out of Paris ahead of the German Army. George's love for his bicycle takes on a whole new significance after reading Borden's book.

''Readers can see that various scenes in the books are echoes of the Reys' past," Borden said. ''Now they have faces and lives. I think that's exciting. I think readers are going to look at Curious George with new eyes."

Mark Feeney can be reached at mfeeney@globe.com.

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