When Wilson checks House after his OD on insulin, the pen light in Wilson's hand changes hands in between shots.
You could not have a crash cart, or even just a defibrillator, in the MRI room. Too much metal with that strong a magnetic field.
When the dancer's heart is being stopped with a defibrillator, the paddles are placed on a non-conductive dressing. No current would flow through her body, and her heart would not stop as shown.