Because Erin Murphy, who played Tabitha, was ill, her fraternal twin sister Diane took her place in this episode. By this time, Erin and Diane didn't resemble each other as much as they once did, and it was obvious to regular viewers of the show that it wasn't the Tabitha they were used to seeing. The producers received several letters asking "Who was that?"
When Uncle Arthur loses his powers,Samantha offers to teach him how to drive. This is a reversal of the season 1 episode, "Red Light, Green Light", where Paul Lynde - playing a driving instructor before he was later cast as Uncle Arthur - tried to teach Samantha how to drive.
Elizabeth Montgomery herself chose the name 'Tabitha' for the name of her TV daughter; actor Edward Andrews had a daughter with that name and Elizabeth liked the 'old fashioned' way it sounded. But at first the name was spelled 'Tabatha' in the credits and Elizabeth disliked it.
The main reason the first few episodes of season 7 were filmed in Salem was because there had been a fire in the kitchen area of the set between seasons 6 and 7; subsequently the set had to be partially rebuilt. This explains the changes in the kitchen in season 7, including a new eating area and the back staircase.