Pumpkin is mentioned in one of Brigg's journal entries, which states that a raider named Chucky, who had been keeping her as a pet, was concerned that she would be eaten by hostile mole rats. The entry implies that Brigg might have killed Chucky.
She is not hostile towards the player and is found locked in a cage. There is no known way to release her without the use of console commands.
There is a dog in The Elder Scrolls IV: Oblivion called Pumpkin, and a fox in The Elder Scrolls V: Skyrim called Pumpkin.