Let me try to explain each of those ideas separately.
The ice method is sometimes used as a form of VAGAL STIMULATION which can be done in a clinical setting to reduce heart rate. It is done when patients are conscious and the electrical conduction of the heart is still able to pump blood to the body.
In a general sense, it works by stimulating the vagus nerve to slow down the impulse telling the heart to beat. There are other ways of performing vagal stimulation to slow the heart, such as having the patient blow through a straw, carotid sinus massage, or having the patient attempt to "bear down" as if they were having a bowel movement. Any of these things can be attempted in a clinical setting to slow heart rate before other, more invasive methods are tried (medications, cardioversion, defibrillation). While vagal stimulation may slow certain varieties of accelerated heart rates (supraventricular tachycardia for example) it is not a substitute for defibrillation. This is because defibrillation works differently, and on different electrical disturbances.
Defibrillation is only used when the heart is beating in one of two specific rhythms; Ventricular Tachycardia and Ventricular Fibrillation. In both of these states, the electrical system of the heart is still sending signals which can be observed on an EKG, but they are not adequate to pump blood, so the patient has no pulse. Basically, at this state the heart is just a quivering muscle which cannot really pump blood in that condition.
When the heart is in VT or VF, defibrillation is necessary. Defibrillation works by conducting electricity through the heart in order to STOP it, not to START it. It works on the principal that the heart is shocked out of the current non-perfusing rhythm with the hope that the body can start it back up again and when it does, it will be in a rhythm that is capable of pumping blood to the body.
If for some reason defibrillation is unavailable, there is also another method called the PRECORDIAL THUMP. It is an absolute last ditch move, done by pounding a fist down on the patient's chest, with the hope that the energy transferred from the hit will work the same way defibrillation does. However, this rarely works.
TV medicine is usually horribly wrong, for instance: you do not shock a flat line, and there is really no reason to inject "adrenalin" or anything else directly into the heart, but on tv they do it all the time for the drama.