The key to understanding the humour in this cartoon is the word ‘spirit’. ‘Spirit’ is an example of a ‘homonym’: a word which has the same spelling and a pronunciation as another word, but with a different meaning. In this case, ‘spirit’ can mean ‘a ghost-like spirit’ or a ‘hard type of alcohol’, for example, whiskey or vodka.
Another example of a homonym is ‘left’
1) Left is the opposite of right