All dogs go to heaven. And so do their masters.

Iwao Takamoto, the animation designer who got his start in the cartoon biz working for Walt Disney before finding fame at Hanna-Barbera Studios creating the lovable Scooby-Doo and other memorable characters, died Monday of heart failure. He was 81.

Gary Miereanu, a spokesman for Warner Bros. Animation, told E! Online that Takamoto was hospitalized for respiratory problems at Cedars-Sinai Medical Center in Los Angeles before he suffered a heart attack.

Takamoto worked right up until the day he died, serving as vice president of special projects for Warner Bros. Animation. He recently storyboarded the 2005 Tom and Jerry animated short The Karateguard, and had a hand in hatching numerous characters for the current Cartoon Network and Kids' WB! animated series Krypto the Superdog. 

He also oversaw the direct-to-video series of his most popular character, Scooby-Doo, the cowardly canine who—with a little help from some Scooby snacks—helped Fred, Daphne, Velma and best bud Shaggy solve mysteries in Scooby-Doo! Pirates Ahoy! and Chill Out, Scooby-Doo, among other recent titles. 

"Iwao Takamoto was not only a tremendously talented designer and artist, he was a beautiful human being," said Sander Schwartz, president of Warner Bros. Animation. "Iwao was always ready with a wide smile, a firm handshake and a warm welcome. Iwao's designs will be his legacy for generations to come. Those of us who had the privilege of working closely with him will miss his mentoring presence, his good counsel and his unparalleled talent and spirit."

Takamoto's death came three weeks to the day of the passing of another animation giant—his old boss, Hanna-Barbera cofounder Joseph Barbera, who died at age 95. 

Takamoto was born in Los Angeles on April 29, 1925, to Japanese immigrant parents. Like many Japanese-Americans, he and his family were sent to an internment camp after the bombing of Pearl Harbor.

His imprisonment at the Manzanar Relocation Center in the California desert proved to be fortuitous for at least one reason. It was there the young Takamoto was introduced to drawing by fellow internees and received some informal training in illustration. After the war ended, in mid-1945, Yakamoto applied for a position with Walt Disney, whose animation house had by then scored major success with Mickey Mouse shorts and such feature-length 'toons as 1937's Snow White and the Seven Dwarves, 1940's Pinnochio and Fantasia, and 1941's Dumbo.

Takamoto was hired as an apprentice to Uncle Walt's legendary "nine old men," the stable of highly accomplished draftsman that included Ollie Johnston, Frank Thomas, Milt Kahl, Eric Lawson and Ward Kimball, who are generally credited with creating some of Disney's most revered classics.

Takamoto assisted on a variety of shorts and full-length Disney features, including 1950's Cinderella, 1955's Lady and the Tramp, 1959's Sleeping Beauty and 1960's One Hundred and One Dalmatians, learning the basics of character design and other hand-drawn animation techniques.

Following Dalmatians, Takamoto left Disney for Hanna-Barbera, a competing cartoon dream factory that targeted the burgeoning television market. Over the next four decades he enjoyed greater responsibility in a variety of positions: from layout artist and production designer to animation director and creative designer on such 'toons as Josie and the Pussy Cats, Harlem Globe Trotters, The Secret Squirrel Show and Johnny Quest.

The artist designed characters for several of Hanna-Barbera's most beloved TV shows, including Astro on The Jetsons and the Great Gazoo on The Flintstones. He also served as a producer on such animated '70s programs as Yogi's Gang, Superfriends, The Addams Family, Hong Kong Phooey, Jabberjaw, Fred Flintstone and Friends and The Great Ape Show.

But Takamoto's biggest success by far was Scooby-Doo. The animator once said he was inspired to draw the talking dog with the voracious appetite after meeting with a Great Dane breeder.

"There was a lady at [Hanna-Barbera] that bred Great Danes," Takamoto once said. "She showed me some pictures and talked about the important points of a Great Dane, like a straight back, straight legs, small chin and such. I decided to go the opposite and gave him a hump back, bowed legs, big chin and such. Even his color is wrong."

He then took the name Scooby-Doo from Frank Sinatra's crooning "dooby-dooby-doo" at the end of "Strangers in the Night," and a cartoon icon was born.

After Warner Bros. Animation bought the Hanna-Barbera library from Ted Turner in the mid-'90s, Takamoto continued working for the company, helping to keep his favorite characters in the public imagination.

Shaggy and Scooby Get a Clue currently ranks as the top-rated Saturday morning broadcast on the CW. Warner Bros. also produced two live-action films based on the character, Scooby-Doo and Scooby-Doo 2: Monsters Unleashed.

Takamoto directed one big-screen feature, 1973's animated Charlotte's Web, and acted as the supervising animation director on 1990's Jetsons: The Movie.

He is survived by his wife, Barbara, and two children, son Michael and stepdaughter Leslie. Funeral arrangements are pending.