When Cole shows Phoebe the ring, she says that her grandmother was married with it six times. In earlier seasons, Grams was said to have been married four times.
When Phoebe stands up in the bathtub, her back is completely dry and soap-free.
In the final scene (Cole and Phoebe in the tub), Phoebe pulls the chain to let the water out and put Gram's cursed ring down the drain. However, after she does this, then talks to Cole, she pulls the drain chain a second time, then puts the ring in the drain.
When Piper takes Tyler to the attic to show him the Book of Shadows, it is laying on a table with a bunch of other books. Throughout the entire series in all other episodes the book is in a place of honor on its own pedestal. There is not even a pedestal in the room.
Piper is mad at Grams for binding their powers when they were younger and eventually comes to the realization that she did it to give them the gift of a normal childhood. But earlier in the series during the first season when the Sisters went back in time, they found out that their powers were actually bound to protect them from the warlock Nicholas.