The order of pages in the Book of Shadows changes. When Phoebe is looking at the entry for Balthazor, the page on the opposite side of the book is the summoning spell. In earlier episodes, the summoning spell was a page turn away and the left page had Phoebe's entry on Belthazor's human half, Cole.
Piper and Phoebe don't seem to instantly recognize Phoebe's younger self when she and Old Phoebe are summoned. You would think they would, since Phoebe and Piper would both know what she looked like as a kid.
Everyone says Paige's promotion is personal gain, but early in the show the rule was stated that you couldn't KNOWINGLY use your powers for personal gain. Paige actually used her powers to help Carolyn, not so she would get a promotion.