A 70 year old patient was treated with a cardioverter-defibrillator because of repetitive syncope and sustained ventricular tachycardia. Six months after implantation 49 shocks were delivered by the ICD while she was cleaning her apartment. Upon interrogation p-wave oversensing during sinus tachycardia was found to be responsible for the inappropriate shocks. The cause of the oversensing was a lead dislodgment caused by a Twiddler s Syndrome. As it turned out in the presented case, the main causes for the Twiddler s Syndrome are patients manipulate the devices and surgeons create oversized pockets. Additional predisposing factors are: psychiatric disease, weight loss, obesity, advanced age, female gender and a loop of the lead outside the pocket. The use of subfascial instead of submuscular ICD pockets may reduce the frequency of this complication but it is still crucial to avoid oversized pockets and to instruct the patients not to "play" with their device.