-Trials and Tribblelations
-In a Mirror, Darkly
All these are considered among the best episodes in their respective series. None of the 4 spinoffs have this kind of homage from each other;
I don't consider these episodes the best. In fact I think they are all pretty mediocre. Trial and Tribbelations is the best of those, but only because of the truly amazing, seamless integration of old and new.