How Green Was My Thumb? - S3-E17
Revealing mistake: When Roy brings in the man with the laryngeal obstruction (partial dental plate), Morton and Early meet them at receiving, then as they rush the stretcher into treatment 1, it's amusing to note that the treatment room across the hall (treatment 2) has room number 412 on it, and even better, treatment 1 itself has number 411 on its door. Obviously the set was prepped for the following shots, when Johnny follows the nurse onto the 4th floor.