This sort of meets those conditions:What show featured 2 guest stars that were main stars together of their own show in which the star of the show in question played a minor recurring character in the 2 guest stars' show?
I can only think of one show.
Spin off shows do not count.
Billy Crystal and Christopher Guest both appeared in the first episode of Saturday Night Live with Howard Cosell, (1975). Cosell hosted the last episode of Season 10 of Saturday Night Live, when both Crystal and Guest were main cast members. Crystal was a guest on Cosell's show; Guest was one of the "Prime Time Players", along with Bill Murray and Brian Doyle-Murray. Cosell played a fictional version of himself in several sketches in his SNL appearance, most notably as the host of "The Run, Throw and Catch Like a Girl Olympics".











