Apart from the two parters, I can think of just once that majel Said "previously on Star trek Voyager" after the opening credits and that was Coldfire to explain what a caretaker was before the audience sat down to watch Susperia run amok.
WHAT A CARETAKER IS!!!!!
They assumed that their audience had not seen the pilot or couldn't remember the plot of the TV show they were watching.
Mean while they needed a Previously on Buffy the Vampire Slayer every week, and it went on for 5 minutes just to keep everything straight, because everything mattered and everything was connected...
Do you remember when Majandra Delphino used to stand in front of a white board and and draw really bad cartoons to flow-diagram explain the Previously on Roswell?
THAT WAS AWESOME!
(Gosh she is so pretty.)