Character mistake: When April goes to see Hank at his motel, he states her romantic feelings for him are a result of "Nightingale Syndrome," however, the Nightingale Effect is caused by the caregiver developing romantic feelings for the patient, not the other way around.
About Face - S4-E6
Continuity mistake: Hank boards Boris' helicopter, but just before he does the helicopter is shown in a wide shot with no one nearby. Hank boards and a guard closes the door from the exterior. Seconds later the helicopter takes off and a wide shot shows no one on the ground. The guard appears out of nowhere and then vanishes.
Trivia: Evan was originally written as Hank's best friend. But when Paulo Costanzo was cast, his physical resemblance to Mark Feuerstein inspired Andrew Lenchewski to turn the characters into brothers.