Old man: He thinks he is wise and knowledgeable, but really he is totally inept. He wore his slippers to work.
Old woman: She looks like a sweet little old lady, but her basket contains a monster that feeds of the fingers of small children. Be wary of old people offering you sweets!
These were for a book, but they didn't get used unfortunately. Which is a shame, but I don't think the publishers would like my 'humorous' character descriptions.