You had warned Astarion not to steal that enchanted amulet off the wizard in Sorcerous Sundries, the library in Baldur's Gate. You told him it was too risky and that they party didn't need an unnecessary fight.
But. As it goes, Astarion didn't listen. The next thing you knew, you heard yelling. One voice was coming from an old wizard and the other was Astarion.
"I don't know what you're talking about, you withered old prune!"
Astarion huffed and turned his back to the wizard, crossing his arms dramatically.
He was always snarky and seemed arrogant, but when he was like this, it was doubled ten fold.
Without uttering a comeback, the old wizard, with a flick of his wrist, cast polymorph on Astarion.
Astarion then turned into a sheep and the amulet he stole, clanked on the floor.
The old wizard grabbed the amulet off the floor, chuckled and left.
All Astarion could do was 'baa' in protest. He was slightly embarrassed to be turned into such a pathetic creature, especially in front of you.