I loved this story as a child and I'm delighted now to see my children enjoying it with exactly the same illustrations. Both children think it is highly amusing when Mog forgets the most simple things and each time Mog does something that's a nuisance (like squashing the flowers in the window-box, or sitting on a hat) they like to shout out 'Bother that cat' with Mr and Mrs Thomas. Basically, in this story Mog foils a burglar through her forgetfulness and gets a medal. My three-year old son is big on cops and robbers and loves the pictures showing the archetypal storybook burglar - stripy jumper, flat cap, torch and a big bag for swag - and is delighted when the police show up. I'm more amused by the burglar sharing a cup of tea with the Thomas family post-arrest. A classic.
& if you enjoy Mog the Forgetful Cat, you might like to try the longer picture book Oakley: The Church Mouse for the same 1970s charm.