Elvis loved the Tonight Show until Johnny Carson said something about him being "fat and forty.” Elvis turned against him after that.
Elvis Presley went on the Tonight Show when Steve Allen hosted in 1956.
While not particularly connected with Elvis, they were mutual fans. Carson did meet with Elvis in 1969 and saw him live in Vegas.
Here are two stories from Alanna Nash's great book, Elvis Aaron Presley Revelations of The Memphis Mafia featured on ElvisInfoNet.com.
Of interest, find out 75 things you may not know about Elvis Presley shared by PopMatters.com.