Carson did it for years. The second chair could be counted on for some off-topic irreverence, and it consistently kept the show from being what all chat shows are now: a forum for selling the product du jour (movie, book). Now, I'm always startled to see line-ups that must include some damned pithy green room chatter, none of which are we privy to, because people in the same building on the same day never speak to one another in front of us. I miss those left-field comments, the sometimes fascinating contretemps and chemistry that would result. People flirted, fought, took sides against Johnny. It was, you know, spontaneous. Now, not so much. Good for Corden.
"I'm a comedian, but in my spare time, things bother me." Garry Shandling