Let's say episode 3 of GAB season 7 just had these cast members...
So short clips of the city of New York would be shown to fill in where other cast members would have been in the opening.
In the final season, the opening theme is slower. There would be no more "classic clips" of the show seen in the opening, as they would be replaced with images taken of New York city with zoom ins, et. (to fill in for timing of the theme song if there was a smaller cast as in this episode, for example.
Let's say in this episode, Nell, Addy, Mama Maybell and Ernie, take Maggie and B.J. to a therapist to save their marriage when it begins to fall apart again. The rest of the cast would be missing, as usual, as there were budget cuts in season 6 and this also happened in that season as well.
This is what you'd call a budget cut episode.