I was once helping in a 5th and 6th grade Sundayschool class, and the whole class was dominated by boys that day. The teacher that I was helping challenged me to make a water fountain in the center of the table, and gave me 10 minutes to do so. The boys in the class were between the ages of 10 and 12, so I knew just what to do. I left the room and returned with a bunch of cups of water, and passed them around. I then told all the boys to take a cup, and had them all take a sip at the same time. Right as they took their sips, I said "I lost 2 pounds peeing this morning." The boys all suddenly spit their water out all around the table in laughter, essentially making an intricate water fountain around the table, fulfilling my teacher's challenge.
This is totally not a true story at all, but you said you wanted to see a funny comment in the morning.