Have i make something wrong or is it a Bug?
You did something very wrong.
You create joints every ticks. Each moment passing by, you're adding new and useless physics elements to calculate.
Simply change the condition "On every tick" by a "On start of layout" and you can have hours of enjoyment with your doll with no slowdown <img src="smileys/smiley4.gif" border="0" align="middle" />