Yes! That is exactly what it means to 'fill in the jokes'.
Think of some of the more famous comedic times such as Dean Martin and Jerry Lewis, or Abbott and Costello. One of the team members would be the 'straight man' and he would deliver the serious line. The other member of the team would provide (fill in) the punchline.
In the Airport films, Robert Stack, Peter Graves, and Charlton Heston would be the straightmen and the audience was left to fill in the punchlines, if they wished.
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