
When Iwao arrived at the studio the senior layout artist was Dick Bickenbach, who was part of Hanna-Barbera on Day One (July 7, 1957), and had worked with Bill Hanna and Joe Barbera at MGM starting in the mid-1940s. Iwao became the head designer in the mid-1960s at the time the studio focused on Saturday mornings. He is known for designing Astro on The Jetsons, Mugger (the Muttley-esque circus dog) in the feature Hey There, It's Yogi Bear, The Great Gazoo on The Flintstones and a Great Dane who needs no introduction.
Iwao (I don’t understand why his name is pronounced EE-WOE) penned an autobiography with Mike Mallory. He talks of his time at Disney and, before that, life in an internment camp where Japanese living in California were forcibly moved after Pearl Harbor lest any of them be secretly in cahoots with Tojo.
This is a thoroughly lazy post as I’ve clipped short segments from the book for those of you would haven’t read it. About his arrival, he writes:
At the time I signed on in 1961, Hanna-Barbera's chief designers were Bick Bickenbach [left], Gene Hazelton, and the artist who really seemed to set the style for the studio, Ed Benedict. Ed had also come from the MGM short cartoon department, but there he had worked mostly in Tex Avery's unit instead of Bill and Joes. I did not have much of a chance to know or work directly with Ed, but I learned a lot just from looking at the work that he did, not so much in regard to his character designs, but his backgrounds. I loved his thinking process, and the simplicity in which he got across his ideas in shows like “The Flintstones.” Ed's designs made the homes really look like they were dug out of a boulder, with a flat granite slab on top, looking like it had just been lowered down there on the head of a dinosaur. The result was almost cave-like, but at the same time strangely modern; a real primitive but fun environment which set the pattern for visual stylings that are still being used today in animation.
One of the originals at H-B was Dan Gordon, who had worked with Joe Barbera at the Van Beuren studio. Both then moved to Terrytoons in 1936 and later did side-work in comics on the West Coast. Dan lost a son in an accidental house fire and his last years were far removed from Hollywood and anything to do with animation. Here are Iwao's stories about Gordon:
Among the hugely creative people who were there in the early years was Dan Gordon, who was a designer, an animator, a storyman, an all-around talent. He had been in the business for decades and was a great gag man, but he also suffered from the affliction that affected so many others in the industry: alcoholism. I don’t really know why drinking was so prevalent within the business, but I've often wondered if it had carried over into film from the newspaper trade. Quite a few of those who went into animation in the early years were cartoonists out of New York, and newspapermen of that era were known for their thirst. Perhaps they carried their drinking from the periodical end of the business into he animation end of it. At Disney’s, a large percentage of the fellows drank quite a bit because of the pressure that they felt. I might run into a group of them at an establishment called Alphonse’s, which was a favorite watering hole, but they would also have open bottles of vodka in their desk drawers in the office.

At the time I was working with him, Dan used to hang out in the Cinegrill, which was a famous club attached to the Hollywood Roosevelt Hotel, on Hollywood Boulevard. Sometimes after a late evening at the studio, I would go to the Cinegrill with Harvey Eisenberg’s son Jerry, who also worked as a layout artist at the studio, for dinner, and invariably Dan would be there, hanging out. We would go over and buy him a drink—Dan’s refreshment of choice was the boilermaker—and on one occasion I remember sitting with him and conducting an impromptu story meeting about how some project we were working on lacked a script. Dan always communicated with little drawings, rather than try to describe what he was thinking, and I remember that his hands were constantly shaking. I wondered, “How the devil is he going to draw anything with his hands shaking like crazy?” But he picked up a pencil, and brought his quivering hand down toward the paper, and as soon as the point of the pencil touched it, everything solidified. His shaking stopped and very quickly a little idea sketch emerged. Despite his drinking, Dan remained full of ideas.
I'm a little disappointed Iwao didn't have anything about Mike Maltese in the book, but he did say this about another former Warner Bros. writer who migrated to H-B after working for John Sutherland Productions:

Hanna-Barbera took some knocks for its limited animation, the only kind practical for television at the time, though it looked an awful lot better than the almost static series for TV that came before. Iwao made this comparison:
Some people have suggested over the years that one did not have to be as good an artist for this style of animation than the full, elaborate Disney style, but that is not the case. Because many of the drawings had to be held on screen for a long time, as opposed to one-twenty-fourth or one-twelfth of a second, the poses had to be extremely accomplished and funny in and of themselves. That takes a lot of talent, and the Hanna-Barbera studio had it, with Bill and Joe themselves right at the top of the list.
Iwao passed away in Los Angeles on January 8, 2007.
You can read his book at Archive.org.