The original Deadline announcement said that the movie will be about two EMTs: one who is on his very last day and retiring, and one who is training to be his replacement. The two have to work on one final 24-hour-hour shift together in order to complete the training, and as one could imagine, any wild thing that could possibly happen does happen. My guess is that means there’s at least one person with something stuck in an orifice, some people in truly perilous situations, and maybe some kind of escaped zoo animal attack. (Maybe a dik dik? It has horns!)
As for the title: a “code 3” is the code in ambulance lingo in the United States for an emergency situation where the lights and sirens need to be turned on and the emergency vehicle needs to travel without delay. (“Code 1” means no lights, no sirens, and “code 2” allows for the lights but no sirens!)