Leo is a kind bloodhound dog who knows the solution to finding things when they're lost. A way is to put things in boxes.

He appears in episode 'Lost Property' when Eva disguised herself as a stripy kitten and said that she lost her ball of yarn to trick Leo and to lure him into the Ever Grey Swamp.

When Eva locked her house, she left Zull and Gort to gaurd him, Leo realises that Zull and Gort don't get along and he made them end up arguing which distracted them for a while and he escaped. He became a pet to Maggie .