Talk shows like Today & The Tonight Show helped put NBC on the map back in television's infancy. Rupert Murdoch, the owner of 20th Century Fox, decided he wanted to follow that path in launching his network.
In October 1986, the Fox network debuted with The Late Show, which made an immediate splash by hiring away comedienne Joan Rivers from Tonight, where she'd been Johnny Carson's designated fill-in. Unfortunately, that decision severed the personal & professional relationships between Rivers & Carson, and the aftermath would also prove costly for both Rivers and her new employers.
For example, an Omaha, Nebraska station refused to carry the show out of loyalty to Carson, who started his television career in the area in the 50's. Regional loyalty isn't as much a problem as the overwhelming national loyalty of millions of viewers, who chose to stick with Carson. After early success, ratings, predictably, began to decline. Rivers clashed with executives behind the scenes, and was sacked after 7 months in May 1987.
That led to a parade of fill-ins, ranging from fellow comedy icon Mel Brooks to original MTV VJ Martha Quinn, less than a year removed from being removed from the then-music channel. As a comic, as she would demonstrate again on Evening at the Improv later that year, Quinn was no Brooks, Rivers, or Carson. Not even close. By the end of the summer, the network thought they had their man in Arsenio Hall, but Hall left after 13 weeks due to movie commitments ("Coming to America", with Eddie Murphy). In due course, the show was finally cancelled, only to be brought back in 1988 with another unknown comic, Ross Shafer, taking over. Shafer's tenure was marked with cast reunions of Gilligan's Island & Batman, but otherwise it was unspectacular.
Rivers & Hall had the benefit of having 70's 1-hit wonder Clint Holmes ("Playground in My Mind") as announcer, and Mark Hudson (yes, one of the Hudson Brothers) as musical director. Holmes was not brought back when the series resumed under Shafer, as I believe Holmes had moved on to Broadway by then, mostly as a playwright.
Here's a sample from the series premiere with Joan Rivers:
With Rivers now in a medically induced coma, according to recent reports, following some heart issues, maybe now might be a good time to remember her at the peak of her powers.