Roger Sweet, the pioneering toy designer credited with creating He-Man and the Masters of the Universe toy line, died Tuesday at a memory care facility in Lake Stevens, Washington. He was 91.

Sweet's wife, Marlene, confirmed to TMZ that he passed away peacefully early Tuesday morning after a prolonged battle with dementia. She had revealed his diagnosis earlier this year, noting a severe fall that caused two brain bleeds and required intensive care before his transfer to the facility. Memory care costs exceeded $10,000 per month, prompting Marlene to launch a GoFundMe campaign in February that raised nearly $94,000 from fans, surpassing its $50,000 goal. The Mattel Foundation contributed $5,000.

Born in 1935 in Akron, Ohio, Sweet graduated from Miami University and the Institute of Design at the Illinois Institute of Technology. His career included design work for Boeing on the 747 interior, as well as products for Rubbermaid, Hoover, and Procter & Gamble.

Sweet joined Mattel's Preliminary Design Department in the 1970s. After Mattel passed on Star Wars toys, which became a hit for rival Kenner, the company struggled with original action figures like Kid Gallant and Robin and the Space Hoods. In 1976, Sweet crafted a prototype by bulking up a Big Jim figure with clay, creating a muscular barbarian he pitched as "power personified." He named the character He-Man for its versatility in any scenario. The figure launched in 1982 and exploded in popularity.

Sweet received substantial bonuses from Mattel, including 50% of his salary for three years during the line's run. He later contributed to Barbie accessories before retiring in 1992 with Marlene and relocating to Washington.

The He-Man toys spawned the 1983-1985 Filmation cartoon "He-Man and the Masters of the Universe," where Prince Adam transforms into the hero by wielding the Sword of Power and declaring, "By the power of Grayskull!" The franchise expanded with spin-offs like She-Ra: Princess of Power, multiple animated series through 2024, a 1987 live-action film starring Dolph Lundgren, comic books, video games, and more.

A new live-action "Masters of the Universe" film, directed by Travis Knight and starring Nicholas Galitzine as He-Man and Jared Leto as Skeletor, is scheduled for release on June 5.

Sweet detailed his experiences in the book Mastering the Universe: He-Man and the Rise and Fall of a Billion-Dollar Idea. He is survived by his wife, Marlene.