Im trying to remember this weird movie... Help....?

Okay not really sure when this movie came out.. and can't remember much of anything about it.. but it was a cool movie. I remember watching it in the mid 90's.. it's freggin weird.. all I can remember is these tenagers are watching tv ( either sister and brother or boyfriend and girlfriend) and they get takin back in time or put into the scenes of the show their watching... but it's weird all I can remember is hearing Three's Company theme song and i remember somebody's head getting chopped off but the movie isn't gory it's more like a twisted humor movie... Please help because im beginning to think i made it up.. lol...