I was cleaning up after a tryout clinic one day at the dance studio where I held the clinics. The dance studio had all concrete floors, which is unusal for a dance studio but they refuse to get dance floors. Anyway, they had panel mats and a port-a-track, which is a full size tumble trak that folds up and can be rolled away for storage ( takes a good 4 strong people to fold up and put away). After the clinic I had to clean up. One of the families trying out had 4 daughters- 2 in the younger clinic and 2 in the older clinic. Mom had asked if the younger two could stay because she had to pick up a bday cake for one of them and I said that was fine as I knew the family quite well. The youngest girl was 4 or 5 and while we were folding up mats she had hid under the tumble trak and we didn't know it. Her older sisters and I finished folding up all the mats and their mom wasn't back yet. Oldest daughter asked if she could do 1 more RO bhs layout on the tumble trak before we put it away and I said 'sure no prob'. Meanwhile, youngest child is still underneath and we didn't know. Oldest tumbles down the trak and lands her layout. When she landed the bed part of the trak sinks down of course and landed on youngest sister's head. Her head hit the steel frame underneath and then bounced off the concrete. Little sister comes crying out from underneath with her hands on her forehead and is upset. I didn't know how bad it was and asked her to take her hands off so I could see what was wrong and her forehead was split clean to her skull and blood sprayed clear to the front of the room (like 15 feet- no joke). She left in an ambulance.
I'm still good friends with the family today and poor kid still has a nasty scar and it happened in 2005.