Conversation so far:
Who does Kermit perform with?
Jim Henson originated the character.
what was his performance about?
CANNOTANSWER.
Are there any other interesting aspects about this article?
veteran Muppet performer Steve Whitmire was named Kermit's new performer.
Why did he need another performer?
Following Henson's death.

Question: When did Henson die?
Self-contained rewrite: When did Henson die?