Back in grade school (and a bit in grade 9, I think) we played a crazy game called Lapte Gros. The name literally means Thick Milk in Romanian, and no, it makes no sense. In any case, it was an amazingly dangerous game, as you can see in the video further down the page.
Regarding the origins, I'm not really sure where it came from. After showing it to Fernando, a friend of mine who is Spanish, he recognized it and remembered playing it back in Spain. Therefore people knew about it in the far Western Europe, as well as in Eastern Europe.
The game is usually played exclusively by boys. One person is chosen to support the team that is "it". He is not on a team, and simply stands up with his hands clasped near his waist, as he will hold the head of the first person on the "it" team. He also acts as a referee.
There are two teams, of between three and five persons each. Any more than that is just silly. One of them is the "it" team and will form a "chain" where each member puts his head between the legs of the person in front of him and holds his thighs for support. The members of the other team jump one by one on top of this chain of people trying to cause them to fall, or "break".
Once the jumping team has all members on top of the "it" team, the first jumper holds either one or two fingers up to the referee. The first member of the "it" team must now guess the number. If he guesses correctly, the teams switch roles. Otherwise, the jumping team gets to go again. The teams can also switch early, if a jumper falls to the ground.
Lapte Gros is extremely dangerous since the players can injure their backs during the impact caused by the landing of a jumper. Also, limbs and necks can be injured by falling off the pile during the jump; especially when played in classrooms near all sorts of sharp corners. All things considered, it's a terrible idea, but it was pretty irresistible back then. The more adventurous kids always played it, while the shy ones stayed back and watched.
Here's a video of it being played. They (it's not my video) seem to play a slightly different version than the one we knew in Bucharest, since someone tries to guess a three, and we chose between one and two. I almost forgot to mention that before jumping, the jumper must yell out "Lapte Gros!" (pronounced LOP-TEH GROSS), which can be heard in the video.