Writers for sketch shows normally have to come up with more then one sketch in their lives to get paid more than once.
Save for the rights they get for the DVD release, or might not if they are working for a given corporation, or might do for the stage show recreation but not the DVD, or might do if the show enters syndication, or might do if the show gets broadcast internationally, or might do if the show gets broadcast online.
Thus we end up in a world where IP law is complex.