Cheaper by the Coven Charmed : Season 7 Episode 3

When Paige and Phoebe summon Grams for Chris's wiccaning, Grams puts a spell on the children to try to end their sibling rivalry, but instead it reverts the sisters back to bickering teenagers. Meanwhile Phoebe, still acting like a teenager, attends an award ceremony with Les, and Leo consults a demonic seer to find out who is behind the attack on Wyatt.