John Redcorn was created in 1997.
John Redcorn
Redcorn Gambles with His Future was created on 2005-04-10.
They never say what tribe he is in. They only say its native to Texas. Actually he is said to be Anastasie.
King of the Hill - 1997 Redcorn Gambles with His Future 9-11 was released on: USA: 10 April 2005
As of the latest episode, no he hasn't. However, Wikipedia says that he will find out about it in the episode "The Honeymooners", which will most likely air on Adult Swim because of King of the Hill's cancellation.
John the Skrull was created in 2006.
Angel John was created in 2009.
Not Now John was created in 1983.
Sheriff John was created in 1952.
John Galt was created in 1957.
Song For John was created in 1969.
John's Children was created in 1966.