Joan Rivers, who once was a frequent guest host of the Tonight show when it was hosted by Johnny Carson, but was never invited to return after she launched her own, short-lived late-night talk show for Fox in the mid-80s, is predicting that Jay Leno's nightly variety show for NBC will be a flop. Meeting with television critics at their annual summer "tour" of fall TV programs, Rivers, who is promoting her upcoming reality series How'd You Get So Rich? , quipped that the 10 00 p.m. will allow America to "get bored more easily and to sleep earlier." She added, "Have you ever heard someone say, "Did you hear what Leno said last night?" Ever?" In 1992, the New York Times reported on negotiations to bring Rivers back to the Tonight show as a guest. Nothing ever materialized.