No, you weren't hallucinating Monday night--that was Joan Rivers at 11:30 on KTTV Channel 11 hosting "The Late Show." Months after the comedian was pulled from the battle against Johnny Carson, Fox Broadcasting is airing reruns of Rivers--and others--and billing it as "Best of the Late Show." "We're running the best of the 'Late Show' and certainly many of Ms. Rivers' shows qualify," he added. Fox has Rivers shows scheduled for Monday and Friday. Also among the best of "Late": Tom Snyder, Buck Henry and Arsenio Hall. The repeat broadcasts will air "indefinitely," a Fox spokesman said, in place of the "The Wilton North Report," which bit the dust barely a month after it debuted. Which means "Best of . . ." will be around until the new network comes up with yet a better idea.