Wen 1 is renting an appartment n gives a key to some1 whos not livin in there does the super have a say in it?:
this situation has nothing to do with a lease...it's your business if you give the key to your apartment to someone, esp for the reason you stated.  no extra person is staying there, it's not a sublet, you're doing nothing wrong...sounds to me like your landlord is way too nosey, you are most def within your rights.