Battery died on my fob one morning. You could separate it and release a physical key to open the door. Then the idea is, you plug the fob into the car to get past the immobilisor and it will start.
Well at 4 in the morning my brain did all that but but the key bit in and twisted. Realizing right as I twisted that it was bad. Fucker was stuck for a good month. Fucked the whole system up too. I had another fob in the house so it was okay