Max Remembers is an episode of Max & Ruby from season two.
Discovering a string tied around Max's finger, Ruby leaps to the assumption that he's supposed to remember something. She takes him through the whole house finding all sorts of things that Max should have done (and doing them for him) until discovering what the string was really for.
A picture Max and Ruby, with their parents appear on a back wall.
This episode is on the DVD Playtime with Max and Ruby