One really neat activity in the SCIS program, I think it was, was called Clay Boats and involved the students in molding a piece of clay into a boat shape to see how many pennies it could hold. The main science concepts were sinking, floating, and density. The idea was to make the boat as large as possible to displace as much water as possible thus allowing it to hold more pennies, but still float of course.
So I selected this activity as the focus for a science ed. professional development session for a group of teachers at a school in Plymouth Vermont I had been working with. Having run out of my regular clay I bought a packet of blue playdo that I thought would be a good substitute for the clay. After fifteen or so minutes introduction we filled large plastic containers with a couple of inches of water and started making our clay boats. To my horror, within a minute of testing the boats in the water the 15 or so teachers' hands had all turned bright blue, as had the water. The playdo was water soluble; a fact that had never occurred to me. In panic, I searched the classroom for a substitute and for some reason, I'll never know how I thought of it, my eyes landed on a box of aluminum foil. Quick as a flash I tore off 12 inch squares of the foil and showed the teachers how they could make their boats using the aluminum foil. The funny thing is that I have used foil every time I have done this activity since as it seems to work much better than the clay.
Another, brief classroom story happened just a few years ago when I was teaching math ed to a group of undergraduates. As I was teaching using the SMARTboard at the front of the class I noticed something fall from the ceiling to my right about four feet from the door. I looked up and saw that a couple of ceiling tiles had been removed for a maintenance project. I then looked at the floor directly beneath and saw a dazed mouse looking around as much as to say "where am I?". The mouse was about six inches behind one of the u/grad's chairs which was as close it had come to landing on her head. As I approached, the mouse found its bearings and disappeared under the classroom door. I followed it out just in time to see it disappear under the door to a fellow faculty member's office. By all accounts it spent the weekend dining on a packet of cookies left on the faculty member's desk.
There was not one "eek" from the students and no-one stood on a chair; how times have changed!