After regaining Vigil's Keep from the initial darkspawn assault there is a kitten located outside the keep in the courtyard, near the northeast corner of the map. You can interact with the kitten and choose to pick it up and keep it; if you do so it is added to your inventory as a gift.
When Anders has a high enough approval rating he will tell you of a kitten he used to own, and you can give him the kitten. Choosing the dialogue option, "He can stay at the keep, then," will net an additional (+2) approval, for a total of +13-17). After doing so the kitten will become a usable item in your inventory, Ser Pounce-a-lot. You can 'use' the item as the Warden or any companion - not just Anders - and he will 'talk' to the kitten, who will meow a response. He can be used in battle as an item, and will revive fallen party members. Any member can use him, but it seems Anders must be a member of the party for this to work (even if Anders is fallen he can be revived by another party member "activating" Ser Pounce-a-lot).
- Amusingly, the program used for lip-syncing means that Anders' mouth will actually move with the kitten's meow.