Called 20 of my freinds that do not know each other. Invited them all to a certain cafe in the center of town, at the same time. Sent a message to all 10 minutes after we had to meet, and voila. 20 different sounds at the same time each sitting at his or hers same table got "APRIL FOOOLS" :)
Nasty I know. But I joined everyone 5 mins later and we had a laugh.