This pun is pretty obvious in meaning, but it does expose an area of English pronunciation that learners often find tricky: stress.
The pronoun ‘nobody’ is a compound of the words ‘no’ and ‘body’ and like most compounds, the stress is on the first item – ‘no’ in this case, with weak second and third syllables, so the likely pronunciation would be /ˈnəʊbədi/ with a schwa on the second syllable. It is possible that some speakers would use the /ɒ/ vowel in STOP on the second syllable too, so /ˈnəʊbɒdi/.
When skeletons complain (as they often do) about having ‘no body’ the stress is completely different. It follows the normal rule of where to place the main stress – the last important word in the unit of speech, in this case ‘body’. So the pronunciation would be /ˌnəʊ ˈbɒdi/ and as the second syllable is now stressed it can’t be a schwa, it has to be /ɒ/.
Compare: /ˈnəʊbədi/ vs /ˌnəʊ ˈbɒdi/
Happy Halloween everyone!