Sir Purssefus or Purrsy (Frank Welker) for short, is Betty's mother's spoiled, surly, beloved Siamese cat. She lavishes him with attention and treats him like he’s Betty’s younger sibling, frequently implying that she loves Purrsy more than Betty. And just like any other spoiled rotten little brat, Purrsy is petty, jealous and conniving. Purrsy once accidentally accompanied Betty on one of her missions, but being a cat has not said anything about it. He tends to cause trouble, but the trouble often backfires on him. He also seems to enjoy the company of Maximus I.Q.. Maximus in turn quickly grew fond of him upon meeting him.
- Purrsy likes to cause trouble and frame Betty.
- On some occasions, Purrsy tends to fake illness, to have either Betty or Miss Barrett do his bidding. Even though Betty knows that he is, however as for her mother, still doubts it.