Subject Object / I or Me -- In incomplete sentance

Hi,
The use of 'I' or 'me' is governed by whether the 'I' or 'me' is the subject or object in a sentence. Eg.
Fred and I went to the cinema.
Fred came to the cinema with me.
What is the correct usage in an 'incomplete' sentence?

'Who went to the cinema?'
'Fred and me' or 'Fred and I'?
Does the correct reply depend on the wording of the question? In the example above, 'Who went to the cinema?', the 'who' is the subject suggesting 'Fred and I' is the correct response, although 'Fred and me' sounds more natural to me. What happens if the cinema trip becomes the subject in the question? Eg.
'The cinema trip consisted of which people?'
By my reasoning above, now that those going to the cinema have become the object, would the correct reply be 'Fred and me'?
Please clarify this for me.
Regards,
..matthew