It may come as a surprise to some fans that Joan Rivers was banned from "The Tonight Show" for years until the late comedian made a brief appearance on a segment on new host Jimmy Fallon's premiere episode.

The Rivers ban had been a result of an icy break-up between her and Johnny Carson, the long-time "The Tonight Show" host who had hired her as permanent guest host until she left the position to star in a short-lived Fox late-night program. Carson never spoke to Rivers again.

Jay Leno, who hosted "The Tonight Show" between Carson and Fallon, upheld the ban,

"I didn't want to [have Rivers as a guest] while Johnny was alive out of respect for Johnny," Leno said in an "Access Hollywood" interview. "I don't think he wanted to see her on the show, and that's why we didn't do it."

Leno admits he never discussed Rivers' ban with Carson, but that there was a mutual, vague understanding.

However, Carson died in 2005, nine years prior to Leno's last "The Tonight Show" broadcast. So, why didn't Leno invite Rivers on the show then?

"It got a little awkward by that point too," Leno explaiend to Access Hollywood. "Joan was sort of going on and on about me and I thought, let's let the ground lie fallow for a while and see what happens, but she always kind of kept it going! And I like Joan -- I mean, that was the first autograph I ever got, was Joan Rivers ... I went to see her at the Chateau de Ville in Framingham [Massachusetts] and we were friends, and by then it just got to be awkward and then we never did it."

For her part, Rivers didn't help matters with her animosity. She spoke to "Inside Edition" following her appearance on the Fallon-hosted "The Tonight Show." 

Mediaite reported that Rivers gave Leno the finger during the interview, declaring, "To Jay! Well, Jay. Twenty-three years. I'm still here, and you're going to be selling cars."

Rivers, who appeared many times on Leno's rival David Letterman's show "Late Show With David Letterman" during the ban, died Sept. 4 at age 81 of cardiac arrest.