I have an orange cat. What colour is my cat? [orange]
The secret password is the first month of the year, but with all letters 'a' replaced with 'z'. Please write the secret password. [jznuzry]
Which is closest to the size of a cat: an ant, a beaver, or an elephant? [a beaver / beaver]
The "take a word, replace some letters" seems like it'd work well to me, since it wouldn't be weak to dictionary attacks or google searches and you can make a lot of variations on it. Also the exact answer doesn't have to be in the question.