A number of years ago, at a service on April 1, I got in the pulpit and told the congregation that it had been a really busy week and I did not have time to adequately prepare for the sermon. So, rather than do a disservice to God's Word by preaching a poor sermon, I invited the people to simply sit and meditate on the day's readings for the next 5 minutes or so. Then I sat down. After about 15 seconds I got up and said, "April fool's!" Some of them saw it coming, and some were getting ready to clean out the parsonage. My little joke was probably worse than the one mentioned above since I did this in the middle of the worship service. As described in the first post what this pastor did happened before worship had (really) begun.
As Margaret Hamilton might say, such things must be done "del-icately."
Marshall Hahn