Other mistake: After Johnny takes Captain Stanley's BP, when Chet tells the guys, "Animal fat is the root of all evil," and also after John jokes, "How to survive on no meals a day," check out Roy's feet because he's wearing shoes (looks like black sneakers) that are below the ankle, with no socks. Then in a few moments they're all dispatched to the 'possible heart attack' and when they're at the scene, while Roy is sitting with the patient, he's wearing socks and his uniform shoes (their tops are above the ankle) as usual.
Other mistake: Roy uses the Biophone when he tells Brackett the vitals of a woman with cardiac symptoms, and then Johnny uses the landline to tell Brackett that there's "Another victim, female, 8 months pregnant, she's gone into labor." Brackett responds, "The mother's probably had an MI... Any cervix dilation on the daughter?" It is impossible for Brackett to have known that the two women are related, let alone that they're mother and daughter.
Other mistake: While Johnny and Roy are with the possible heart attack, they've patched her in for the EKG, and in the base station room Brackett looks at the EKG strip and the unit's monitor, then it cuts to a closeup of the Datascope monitor, even though the Datascope is not actually in the ER's base station room.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy