en.wikipedia.org/wiki/George_Jetson

The wording here is historically inaccurate. Hanna-Barbera Productions was set up in 1957, so it was only about 32 years old in 1989, not 50. TV Guide's description of the 1989 special explicitly says it was "celebrating 50 years of William Hanna and Joseph Barbera's partnership in animation" and that it covered the history of Hanna-Barbera Productions, which was set up in 1957.

So the special was about the pair's 50-year animation partnership/career span, not a 50th anniversary of the Hanna-Barbera production company itself.

Contemporary reporting and later coverage of the casting dispute show that Morey Amsterdam was originally slated to play George Jetson before George O'Hanlon was hired. That means the character and role of George Jetson already existed when O'Hanlon joined the production.

So while O'Hanlon certainly became the best-known voice of George Jetson, the claim that he "granted his name to the character" is inaccurate: the character was already named and cast before O'Hanlon replaced Amsterdam.