I have, on more than one occasion, used a "tick-tock" clock effect, running continuously with a shout dropped on with various station positioners every 90 seconds to two minutes. It will be "Q102" the first time, then "Z102" the next, "X102" after that, "K102", etc. Good luck figuring out what I'm going to do after that runs for a week or more non-stop.
I also have done several days of non-stop novelty songs, and once had a loop of Weird Al parodies repeating over and over.
When WXXY in Chicago did the original Eighties Channel, they had 24 hours of television theme songs before launching.
I always wanted to do a format flip after a nationwide EANS test. Interrupt the old format for the test, during which I guarantee the audience will be tuning all over the place trying to find something other than that ... then when the test is over they would be unable to find their old station because the new format launched after the test. 😈