Some kind of electric problem help !

I plugged in my amp (i didnt even turn it on) and my whole car (92 g20) went willy-nilly . For one i cant start it , everything powers up but the engine never turns , i noticed the check enging light and the battery light on , and one time while trying to start the car the wipers came on (no i wasent hitting the lever) i got the battery checked (A ok) , i checked all the fuses (A ok) , and the security , interior lights , radio , and the power antenna , stopped working also .... i unplgged the amp , and tryed a hole bunch of things to no avail , what is wrong ?

~CzeXenViRii