One night, in Larry and Nina's room, a mural grew.

A joyful procession - a dog, two boys, two birds, a lion, a girl, a bear, and a sun - was being painted by a dear family friend, who spread paper and paint jars on the floor and sometimes stood on their beds to work.

It was 1961, and the family friend - Uncle Moo Moo - was Maurice Sendak, 33.

Fifty years later, the mural - in two hefty slabs - has made its way from the 13th-floor apartment overlooking Manhattan's Central Park to a new home: the Rosenbach Museum and Library in Center City, which houses Sendak's papers, books, art, and ephemera.

"As a kid, it was just an amazing experience," said Larry Chertoff, 55, who with his sister Nina, 53, donated the mural in memory of their parents, Roslyn and Lionel Chertoff, and Sendak's longtime partner, Eugene Glynn.

"He just decided to do this," Chertoff said of the mural. "It was really sort of a very natural outgrowth of their friendship and hanging out together."

The Chertoff Mural is the only one known to have been painted by the famed children's author and illustrator, whose books include the Caldecott Medal-winning Where the Wild Things Are. ("That very night in Max's room a forest grew.")

Conservator Cassie Myers is restoring the 4-by-13-foot work inside the Maurice Sendak Gallery, using a scalpel to remove beige wall paint that house painters had applied in and around - and ever so slightly overlapping - the characters. She will fill in cracks, unite the two sides, and restore parts of the mural, such as the girl's face, where paint has flaked or loosened.

Not quite a wild rumpus, the procession of whimsical characters - who look familiar because they would find their way into some of Sendak's work - was painted on a wall leading to a window overlooking the exact midpoint of Central Park near West 84th Street.

"It was sort of a parade, with Jennie the little terrier in the front," said Chertoff, whose bed was near the window, right under the terrier. "It was like they were going to the park, sort of suspended in air, but grounded by the geometry of it. It was very soothing."

The first boy plays a drum, the second a trumpet, with eyes closed and heads thrown back, their right feet up in mid-march. The lion wears a party hat and holds an umbrella - with the words Larry and Nina - in his tail. The girl is in full dress-up - heels, gown, jewelry - with a flag in one hand and a rope leading to the top-hatted bear in the other. An ochre-and-yellow sun shines at right.

Jennie was Sendak's terrier, who already had appeared in the book Kenny's Window and would show up in Where the Wild Things Are in 1963. And the bear echoes Sendak's illustrations for Else Holmelund Minarik's Little Bear series, begun in 1957.

The girl resembles Rosie of Really Rosie, which would come later; Nina Chertoff said, "I thought it was a little bit me." Her brother went back and forth, but ultimately settled on the boy with the trumpet as the character he identified with most.

When their mother died a few years ago and they were in the process of relinquishing the apartment, Nina Chertoff began exploring ways of ensuring the mural could survive.

"I knew when my mom was aging and dying we would have to make a decision about what to do with the mural," she said. "Otherwise, they would just paint over it because they wouldn't know what to do with it."

She got in touch with the Rosenbach and contacted the owners of the apartment building. Everyone agreed they could, and should, cut the wall out and replace it.

"They let us remove the wall," said Nina Chertoff, a literary agent and author of books about collectibles. "It was one of those moments in life where everybody did the right thing."

Her parents, Glynn, and Sendak had been great friends in the Upper West Side intellectual bohemia of the day. Glynn and Lionel Chertoff were psychiatrists; Roslyn Chertoff was a social worker. They played Scrabble, shared meals; Larry Chertoff remembers their laughter coming from the dining room long after he had gone to bed. Only Sendak, 82, survives.

The Rosenbach, with its massive Sendak collection, was a natural choice to house the mural. But getting it to the Delancey Street museum took three years - more even than the "in and out of weeks and almost over a year" of Max's Wild Things sailing trip.

In New York, it took a week - and a helpful vertical crack between the girl and the lion, the result of a heating pipe inside - to cut out the wall and carry it out of 241 Central Park West. The doormen cheered as the two sections, weighing 1,400 pounds, departed.

For the next three years, the mural sat face up on a special table built in the converted horse stables of Milner & Carr Conservation on Cadwallader Street in North Philadelphia, awaiting funding, nerve, and expertise. (The cost of the restoration project, including both moves, will total $200,000.) Treated to relax the paint's brittleness, it was covered with muslin, the figures silhouetted.

It was briefly turned facedown, in order to smooth over the back (the living-room side). Finally, its weight having been shaved to about half a ton, it was loaded Jan. 19 into a white box truck and secured. The truck, with its whimsical band of marching characters on board, took its own charming, if nerve-racking, ride through the city, ending on tiny, snow-covered Panama Street behind the Rosenbach (where, of course, a garbage truck immediately tried to get down the same alley).

Once inside, the mural was wheeled and raised by pulleys, ropes, chains, and men, and finally lifted onto a specially built half-wall. Alas, when it settled onto its new base, a small horizontal fissure about a third of the way down one side opened. But all in all, there was relief.

"We're amazed that chunks of plaster didn't fall off," said Rosenbach curator Judy Guston. "We were very, very nervous over attempting this. But it arrived in one, or should I say two, pieces."

The Chertoff children had always treasured the mural, though Larry admits to throwing a ball against it on occasion and only rarely wondering if he had outgrown it. Nina still smarts at her move to the maid's room by the kitchen when she got older.

"We all loved the mural," said Larry.  He brought up another book that Sendak illustrated, The Moon Jumpers, and said: "I see a link with that a lot. The kids go to the park and jump around at night. I imagined these characters would go to the park and jump around."

Starting this week, the Rosenbach will allow the public to view the restoration on most Wednesdays for an hour at noon and again at 6 p.m. The work is expected to continue until March, when the mural will be put on permanent display, with touch screens and a video of its odyssey. Sendak is expected to visit from his Connecticut home.

Already, Myers said, the removal of the house paint has revealed more of the mural than had been seen in years.

"I can see this little hair coming to be revealed," she said last week, scalpel and solvent in hand. She'd already scraped to reveal a fuller outline of dog hairs and nose.

The mural, it seems, is still growing. "She's definitely much more in motion," Guston said of Jennie. "You see the way Maurice draws, with a lot of line. It gives her a lot of dogginess."

Larry Chertoff said that as a kid, he had tried to tell the painters not to paint between the figures, but that nobody had paid attention. (He and Max, he's certain, have a lot in common. "You know, they didn't listen to me," he said.)

The beauty of growing up under that mural is still vivid, and the Chertoffs are pleased to share it.

"Who would have thought when you were standing in front of it in 1961 or 1962 that it would be in a whole new place with children walking in and out to see it?" Nina said. "It feels so right to me."