If a person is faking being nice to someone then they do not have a warm heart they have a microwave heart. The heat of the heart and the niceness of the person are both being faked!
A teacher passes by person 1 and 2 (they both hate each other) in the hallway. Person 1 kicks person 2.
Person 1: Oh my god! I'm so sorry! Did I hurt you?
Person 2: Screw you with your microwave heart!