The first two sometimes work as furi (giving the audience a sense of expectancy to the story line) for ochi (there are some cases in which the three serve as 'furi, ko ochi [small punch line], and o ochi [big punch line]'.)
そのうち最初の2つは最後のオチのフリとして用いられる（「フリ・小オチ・大オチ」の例もある）。