Howard Stern went on Conan's old show over three years ago, as seen below, and warned him that Jay Leno may not want to leave "The Tonight Show."
"I don't see this guy leaving and letting you walk in. I'm concerned about you," Howard tells him.
He then jokes that Leno "is a guy who stares at the wall ... and waits to go to work. He doesn't do anything but work."WATCH: