Conversation so far:
Who does Kermit the Frog perform with?
Jim Henson originated the character in 1955 on his local television series, Sam and Friends.
What was Kermit the Frog's performance about?
Jim Henson's Kermit the Frog was coming out of his own personality—was a wry intelligence, a little bit of a naughtiness, but Kermit always loved everyone around.
Are there any other interesting aspects about this article?
Following Jim Henson's death, veteran Muppet performer Steve Whitmire was named Kermit the Frog's new performer.
Why did Kermit the Frog need another performer?
Steve Whitmire seemed to imply in a blog post that Jim Henson had asked him to assume the role before he died.
When did Jim Henson die?
1990

Question: Which appearance had he had before his death?
Self-contained rewrite: Which appearance had Jim Henson had before his death?