What is the name of that movie and sequels; title ends in "-er"; bright neon green clear plastic dvd case; main character is a scientist with glasses, lab coat, dark short haircut, he's intense, social misfit; he creates a neon glowing green liquid, in a syringe; there's a cut off head that talks and tries to pick up ladies wagging his tongue; Please help me remember the name of this cult movie/s from the ?1980s? Thank you.