Paul McCartney is now a children's book author. The 63-year-old singer entertained a young group of cute but squirmy elementary school students Thursday by reading an excerpt from his new book "High in the Clouds" and answering questions.

On Saturday, the rock star will provide the first-ever live wake-up call to the crew of the International Space Station.

The reading got some unexpected responses from the young audience.

In the first six pages of McCartney's book, about an industrious squirrel named Wirral (named after McCartney's hometown), Wirral's mother is crushed to death by a tree knocked down by nature-hating developers. From there, he sets off for the mythic animal-loving land of Animalia.

"Why did the author make such sad stories for children?" asked one perplexed little boy.

Caught off-guard, McCartney wrapped his arm around the boy and joked, "To make children cry."

"But cheer up. It's going to be all right," he quickly added.

McCartney co-wrote "High in the Clouds" with author Philip Ardagh, who was brought in after a first draft to "finesse" the book, McCartney told The Associated Press in a phone interview before the event.

The story was his own idea, McCartney said, and was inspired by his collaboration nearly 10 years ago with animator Geoff Dunbar on the animated short "Tropic Island Hum." Dunbar also illustrated "High in the Clouds."

"It's been my ambition for about 30 years to do a full-length animation film," McCartney said. The book became a substitute for a script.

The rock icon said he's never read the book to his three grandchildren or his 2-year-old daughter Beatrice. Beyond the initial death sequence, the story "does get happier," he said.

"I'd skip over that bit, with very little kids... My little one's too little. She likes the pictures though," McCartney said.

McCartney also is "psyched" to become a human alarm clock for astronauts.

On Saturday, McCartney will provide the first-ever live wake-up call, two songs, to the crew of the International Space Station from his concert in Anaheim, Calif.

"I'm singing 'English Tea' from my new album 'Chaos and Creation in the Backyard.' I have a cup of tea in the morning, so it's something good to wake up to," McCartney said.

On Aug. 9, NASA jolted awake the crew of space shuttle Discovery with the Beatles classic, "Good Day Sunshine." Since then, McCartney has projected footage of the crew during his current U.S. tour.

Around 9:55 p.m. PST, he will serenade NASA astronauts Bill McArthur and Valery Tokarev with the same tune, broadcast live on NASA TV.

"It'll be an out-of-space blast. Lots of puns intended," he said.