Roger Sweet, the toy designer best known for creating the iconic character He-Man, has died at 91.

Sweet's wife, Marlene, said her husband had died at a nursing facility on Tuesday morning after a battle with dementia, according to TMZ.

Sweet was a longtime lead toy designer at Mattel in the 1970s and '80s, and during that time he created the muscle-bound He-Man character in 1981, as well as a wider fantasy and science-fiction universe revolving around him with the Masters of the Universe line of toys, which debuted the following year. 

Earlier this year, Sweet and his wife were forced to create a GoFundMe to combat the mounting costs of his healthcare needs following his dementia diagnosis. 

She revealed in February that he had a serious fall while out on a walk, and his subsequent stay in the intensive care unit revealed that he had suffered two brain bleeds.

Marlene shared with Roger's fans that doctors had recommended he move in to a memory care facility to manage his dementia symptoms and allow him to be 'monitored and safe.'

'Roger is now nearly 91 years old and sadly has dementia,' she wrote at the time. 'His illness has continued to progress, and I have done all I can to take care of his needs at home.' 

He-Man emerged in a roundabout way as a response to Mattel's lack of foresight when it opted not to create a line of toys inspired by Star Wars a year before the iconic blockbuster's 1977 release.

Following Star Wars' runaway success, and in the face of the enduring popularity of toys inspired by the film series, Mattel tried to correct the error by developing its own line of genre-inspired action figures. 

Sweet eventually gave the toy brand what it was looking for with He-Man after it had launched several uninspired toy ideas.

Sweet is widely credited with pitching the He-Man design to Mattel, which he believed could be popular because the muscular figure could appeal to children even without the context of his backstory and the surrounding universe of secondary characters.

However, the character's creation has been disputed, and some Mattel designers later claimed that Sweet's prototypes had been inspired by fantasy sketches made by Mark Taylor, a packaging designer at Mattel.

Prior to his work at Mattel, Sweet was a designer at the industrial design firm Walter Dorwin Teague Associates, where he handled projects for major companies, including Boeing, Hoover and Procter & Gamble. 

Sweet had recently moved into a facility to receive full-time care when his wife launched the GoFundMe. 

'He has only been there a few days and his mental decline is sadly continuing. It is devastating to see this happening,' Marlene wrote. 

His wife – who had been married to Sweet for almost 40 years – noted that monthly costs amounted to over $10,000 monthly 'for a patient in his condition' and the services were not covered by Medicare.

'So I am reaching out to all the HE-MAN fans for help with these bills. Any donation will be greatly appreciated and will ease the burden of this new expense,' she added.

In her message on the GoFundMe, she talked about Sweet's impact on the toy industry during his career, such as being 'a toy designer at Mattel for over 15 years.'

'Roger designed and named the original He-Man character, and worked for years with other designers to create all the other characters and playsets that enthralled kids for so many years – and still do today!' 

Before his health battle, Sweet had the chance to meet a number of fans at events and conventions over the years. 

'I was able to accompany him to several, and it was fun to see him interacting with HE-MAN fans,' his wife wrote.

As of Tuesday evening, donations had reached over $93,700, almost doubling the original goal of $50,000. Among the list of donations was a $5,000 gift from the Mattel Foundation.

After Sweet created He-Man and Masters of the Universe in the early 1980s, the characters were repurposed for an animated series, He-Man And the Masters Of The Universe, which aired on television from 1983 to 1985. 

The movie He-Man And She-Ra: The Secret Of The Sword was released in 1985, which resulted in a spinoff animated series, She-Ra: Princess Of Power. 

Most recently, Sweet's He-Man and Masters of the Universe toy line have been adapted once again into an upcoming superhero film titled Masters Of The Universe. 

The movie – which was directed by Travis Knight and stars Nicholas Galitzine as He-Man – is set to hit theaters on June 5. 

The cast also includes Camila Mendes, Jared Leto, Idris Elba, Alison Brie, Morena Baccarin and Kristen Wiig.  

According to the film's synopsis, 'A young man on Earth discovers a fabulous secret legacy as the prince of an alien planet, and must recover a magic sword and return home to protect his kingdom,' per IMDb. 

Amazon MGM Studios dropped the first teaser trailer of the project in January.  

Dolph Lundgren previously took on the role of He-Man in the 1987 film Masters Of The Universe, which costarred Courteney Cox, Frank Langella and James Tolkan.