Currently the best pet to sacrifice for Pet Slots (with Brown Mouse and Grey Mouse being 2nd and 3rd). Starfish does not give bonus exp to other pets. Grey Mouse and Brown Mouse has the same mechanics, although the mouses gives bulk exp after some time. Starfish gives approx. 3,600 exp every 10 minutes, significantly higher than Grey Mouse's 500 exp every 10 minutes. Starfish gives approx. 2,880 exp every 8 minutes, significantly higher than Brown Mouse's 750 exp every 8 minutes. Unconfirmed if intentional but Starfish does not use its passive ability when it reaches 0 hunger.