Dowager Hatt in CGI
Mrs. Dowager Hatt is the Fat Controller's mother, and Stephen and Bridget Hatt's great-grandmother. She first appeared in the fifth season episode "Gordon and the Gremlins", and has made several appearances since in the sixth, ninth, and twelfth seasons.
She owns a Dalmatian, which she renamed "Gremlin" after her adventure in the aforementioned episode.
Gallery
Dowager Hatt at her birthday
Dowager Hatt among the villagers
Dowager Hatt among the passengers