Conversation so far:
When did Johnny Carson go on radio?
Carson began his broadcasting career in 1950 at WOW radio and television in Omaha.
What did Johnny Carson do on television?
Carson soon hosted a morning television program called The Squirrel's Nest.
Did Johnny Carson do any other television shows besides The Squirrel's Nest?
Carson hosted several shows besides Carson's Cellar, including the game show Earn Your Vacation and the CBS variety show The Johnny Carson Show.

Question: When did he join television?
Self-contained rewrite: When did Johnny Carson join television?