I love the 'nope, we do know where babies come from' or 'must have been an immaculate conception we think' or 'yep it was an accident...he just slipped in whilst in bed one day'
And for the second question say 'as long as it looks like DH and not the post man then I'll be happy and relieved' in a secretive tone if DH is nearby or 'hoping for a puppy...they are so cute and cuddly'

You'll always get someone making a comment...usually its just to make conversation and they don't really think before they say it.. Sort of just automatic.